Nuclei make up 99% of the mass in the visible universe, and all but the lightest nuclei are produced in cataclysmic stellar events such as supernova explosions and neutron star mergers. Every proton (and neutron) within all nuclei is governed by QCD, the theory of quarks, gluons, and their interactions. Understanding the amazing world inside a proton requires tremendous technical capabilities embodied in large accelerator facilities and advanced detector technology, as found at the world-class facilities of Jefferson Laboratory. These capabilities enable us to understand how QCD supports the dynamical generation of bound states with a rich variety as seen from data. Interestingly, the more closely one peers into a proton (with higher-energy electrons), the more complex the emergent phenomena one measures. Tying these measurements to theory often requires models informed by LQCD calculations. Furthermore, JLab’s experimental capabilities, using parity violation, have recently enabled a precise measurement of the thickness of the neutron skin in Pb which has implications in the astrophysics associated with neutron-star mergers. This interplay is but one demonstration of how the world of the small, even at the proton level, affects the most violent of collisions in the universe.

While the Standard Model of particle physics is one of the most successful constructed theories in history, several questions remain unanswered, such as the nature of dark matter, the neutrino mass mechanism, the matter-antimatter asymmetry and elemental abundance in the universe. All of these are intimately intertwined with the electroweak interaction responsible for free neutron and nuclear beta decays, making them an ideal laboratory for precision studies to unearth hidden features of Beyond Standard Models physics. In this talk, I will present a brief overview of recent theoretical and experimental progress in this vibrant field, sketch the impact and status of the Nab experiment and show how quantum sensing technology can open up a promising new direction. 

In a talk that I am hoping will quickly morph into a free-flowing Q and A session, I will discuss the roles of journals in general and PRL in particular in disseminating physics results through a cascading sequence involving journal editors, referees, conference chairs, journalists, department chairs, deans, funding agencies, and others. While some of the essential tools of physics dissemination are unchanged, the arrival of social media, search engines, and electronic repositories have us in a state of flux.

The Standard Model of particle physics has been a crowning achievement of fundamental physics, culminating in the discovery of the Higgs boson in 2012. As a quantum theory of the building blocks of matter and forces, it has been one of the most successful theories in science. The recent measurement of the mass of the W boson disagrees with the theory prediction. This upset to the Standard Model may point towards exciting new discoveries in particle physics in the coming years. We will discuss the Standard Model, the crucial role of the W boson, and how it has become the harbinger of new laws of nature.

Motivated by advances in the field of active matter where non-equilibrium forcing has been shown to activate new assembly pathways, here we study how  non-equilibrium driving in prototypical   memory formation models  can affect their information processing capabilities. Our results reveal that activity can provide a new and surprisingly general way to dramatically improve the memory and information processing performance of the above described systems without the need for additional interactions or changes in connectivity. Non-equilibrium dynamics can allow these systems to have memory capacity, assembly or pattern recognition properties, and learning ability, in excess of their corresponding equilibrium counterparts. Counter-intuitively, in some cases, dynamics with non-equilibrium noise-sources can even have a higher memory capacity than  zero temperature equilibrium systems that are not subject to any noise.  Our results demonstrate the  generality of the enhancement of memory capacity arising from non-equilibrium, active dynamics. These results are of significance to a variety of processes that take place under nonequilibrium dynamics, and involve information storage and retrieval, as well as in silico learning and memory forming systems for which nonequilibrium dynamics may provide an approach for modulating memory formation.

During the last century, particle physicists have formulated and tested a “Standard Model” of fundamental particle physics.  This model has been extremely valuable in successfully making precise predictions for thousands of experiments.  Still, physicists know this model is incomplete!  For example, through many astrophysical observations, we know that the source of a large fraction of the energy in the Universe is due to particles and forces beyond what is included in the Standard Model.  This is a pretty big missing piece, but there is more!  We also don’t understand the structure of the Standard Model, or the reason we observe a matter-dominated Universe – why not antimatter?  These mysteries (and others) mean that there is certainly “New Physics” waiting to be discovered if we do the right experiments!  Where is the New Physics hiding?  We don’t know.  I’ll review several ongoing experimental efforts aimed at answering some of these big fundamental mysteries.

Recent observations of black holes and neutron stars through gravitational waves allow us to explore the novel strong-gravity and extreme-density regime. In this talk, I will explain how we can use gravitational waves from binary black hole mergers to probe gravitational physics and those from binary neutron star mergers to study nuclear physics. For the former, I will focus on a theory beyond General Relativity motivated by string theory while for the latter, I will investigate the presence of solid quark cores inside neutron stars. I will also comment on how we can use gravitational waves from binary white dwarfs, expected to be detected with future space-based detectors, to learn astrophysics.

TBA

Atom interferometers are a type of quantum sensor useful for navigation, geographics, and tests of fundamental physics. We report on recent progress in three areas: a trapped-atom Sagnac interferometer for rotation sensing, the use of atom interferometry to measure "tune-out wavelengths," and a demonstration of atom interferometry in the Cold Atom Laboratory on the ISS. These efforts are representative of the types of efforts begin pursued in the field, including pushing towards practical applications, pursuing basic science, and technology demonstrations to support future applications and science.

The search for dark matter is ever-evolving and a number of experiments are underway to search for the constituents of dark matter across a vast range of masses. A largely unexplored regime is that where light dark matter particles, with masses between the electron and proton masses, may interact feebly with ordinary matter. I will discuss how small accelerator experiments can produce these dark matter candidates by scattering energetic particles on a fixed target. I will focus on the DarkQuest experiment at Fermilab that uses a proton beam and builds off of an existing detector and accelerator infrastructure. I will also describe how an electron beam can be complimentary used in the Light Dark Matter experiment (LDMX) at SLAC. I will explain the design and challenges of these experiments and their prospects for characterizing a dark matter signal in the near future.

The discovery of gravitational waves, predicted by Einstein in 1916, is enabling both important tests of the theory of general relativity, and represents the birth of a new astronomy. Modern astronomy, using all types of electromagnetic radiation, has giving us an amazing understanding of the complexities of the universe, and how it has evolved. Now, gravitational waves and neutrinos are beginning to provide the opportunity to pursue some of the same astrophysical phenomena in very different ways, as well as to observe phenomena that cannot be studied with electromagnetic radiation. The detection of gravitational waves and the emergence and prospects for this exciting new science will be explored.

I will introduce, for those unfamiliar with general relativity, the notion of the expansion of space, before going on to discuss a 5 sigma discrepancy between two inferences of the rate of that expansion today. One of those inferences is highly indirect and model dependent, relying on measurements of maps of the cosmic microwave background (CMB), a thermal relic of the hot big bang. I will explain what the CMB is, and show how well our standard cosmological model describes its statistical properties, and how we can use that model to infer the expansion rate today. I will then describe a symmetry under a scaling transformation of all relevant time scales in the problem that can potentially be exploited to reconcile the two inferences. Significant constraints on such a solution come from measurements of the CMB energy density and the abundances of light elements produced in the big bang. The former constraint can be circumvented by use of a ‘mirror world’ dark sector — a copy of the standard model of particle physics with little to no interactions with standard model particles other than via gravity.

Much of the current research in quantum magnetism is motivated by the search for an elusive quantum spin liquid (QSL) state of the magnetic matter. A salient feature of this entangled quantum state is the presence of fractionalized elementary excitations such as spin-1/2 spinons, interactions between which are mediated by the emergent gauge field. 

In my talk, I provide a historical perspective on quantum spin liquids and shed some light on the origins of  this ``weird” idea. Following a brief summary of the current state of affairs in QSL research, I describe  how QSLs respond to the magnetic field and demonstrate surprising similarity of the described response to that of neutral Fermi liquids.

I illustrate these theoretical ideas with a recent electron spin resonance measurements on quasi-one-dimensional antiferromagnet K2CuSO4Br2. The experiment leads the first-ever spectroscopic determination of the (backscattering) interaction between spinon excitations of the quantum spin chain.

I will discuss what recent research says about the science of effective mentorship and how we can learn to do it better. We will focus on 2 competencies - aligning expectations and maintaining effective communication - through some guided activities. I will give you examples of strategies and resources that can help you become a more effective mentor and mentee.

Most of the physics students will work in industry instead of academia after they got the degree (BSc., MS, or Ph.D.)

The speaker will share his personal 30 year experience of working in a small tech company after his post-doc period, including changes and challenges of culture, daily life, responsibilities, etc.

Advice will be discussed with the audience how meet the challenges.

The speaker’s main tasks were to develop ultra-low temperature facilities from 300mK to 10mK. Along with the speaker’s career growth, examples of his achievements are presented.

A brief business summary of the speaker’s company, before and after COVID, is presented at the end of the presentation.

Saturn's moon Titan is a geologically and meteorologically active world seen as a potential location for the development of life. While we cannot immediately answer "Is there life on TItan?" or even "Are there life-forming reactions occurring?" we can take a step back and investigate a more foundational question: "What chemistries are occurring?" The answers to this question are stepping stones to understanding broader processes such as weather cycles, geology, and potentially organic reactions. We attack this question using molecular dynamics simulations. By identifying molecules that cluster or exhibit other interesting behaviors, we hope to identify possible sites for interesting chemical reactions that could produce large or prebiotic molecules, as well as characterize those reactions.

The task of the field of nuclear physics called femtography is to image the internal structure of strongly interacting particles, from single protons and neutrons to atomic nuclei. Protons and neutrons are composed of quarks and gluons, but the precise spatial arrangement of the two valence up quarks and one valence down quark, along with the sea quarks and gluons that contribute half of the momentum, remains unknown.  A compelling method for deriving dynamical information about the internal structure of the proton is through the use of generalized parton distributions (GPDs).  Two-dimensional Fourier transforms of GPDs provide insight into matter, charge, and radial distributions of the quarks and gluons inside the nucleon.  We present an explicit calculation of such transforms in a spectator model framework using parametric analytic forms of GPDs, originally constrained using deeply virtual Compton scattering and lattice QCD data.  We compare the valence quarks to the gluon distribution through, i.a., average radii, a notion of distance inside the nucleon, and we present a novel result for the radius of the gluon density.

Recent developments in two-dimensional (2D) magnetism have intensified the research on novel van-der Waals magnetic materials to explore new magnetic phenomena in the 2D limit. Among 2D magnetic materials, one model system is metal thiophosphates MPX3 (M = transition metal ions, X = chalcogen ions) in which the antiferromagnetic (AFM) properties are highly dependent on the choice of transition metal M. The van der Waals-type crystal structure allows the mechanical exfoliation of bulk crystals to obtain atomically thin layers. In MPX3, the AFM ordering is found to persist down to the atomically thin limit, making them a promising candidate for future device applications. Furthermore, the layered structure also permits the inter-layer intercalation, which is an effective way to tune the properties. With this motivation, we performed Li and Fe intercalation in NiPS3 by using electrochemical technique. In this method, the electrical potential causes electrons to flow from anode to cathode through the circuit within the battery leading to the intercalation of intercalant ions between the layers of the host sample as shown in figure below. By tuning the amount of charges intercalated during electrochemical intercalation, the number of intercalated ions in the host single crystal can be controlled. NiPS3 exhibits AFM ordering below TN = 155 K and the spin-flop transition above μ0H ≈ 6 T. The goal of this project is to intercalate different Li and Fe content in NiPS3 single crystals and characterize their magnetic properties. Mainly, we will focus on the tuning of the ordering temperature and the spin-flop field of pristine NiPS3. In addition, the transition from AFM state to other states such as ferromagnetism is also one important direction of this project. Li intercalation was found to increase the magnetization value of NiPS3.  Future work will consist of characterizing the changes in the magnetic ordering of Fe intercalated NiPS3 and extending the investigation of Li intercalated NiPS3.

The landscape of physics research is changing due to the rapid advancement in computing. Traditionally, science is done through observation and experimentation.  While there is no indication yet that this trend will change overnight, there is an increasing likelihood that methods in physics are changing in a way that we must prepare for. New technology, new methods, and new instrumentation must be brought to the forefront to take advantage of the rapid evolution of artificial intelligence and its ubiquitous pervasiveness in all aspects of research and life.  I briefly review some of the advancement in machine learning and how these developments are changing our field using examples in Spin Physics from the recent past, the present, and near the future.

Gravitational waves have been detected from the mergers of nearly ninety binary black holes during the first three observing runs of the Advanced LIGO and Virgo detectors. In this talk, I will discuss these detections and their implications for understanding fundamental properties of matter and spacetime in two contexts. First, I will review a nonlinear effect in general relativity called the gravitational-wave memory. The effect is characterized by a lasting change in the gravitational-wave strain produced by the energy radiated in gravitational waves. I will describe how this effect is related to the infrared properties of gravity, how the memory effect can be measured with LIGO and Virgo, and how new types of memory effects have been recently predicted. Second, I will discuss how dense distributions of dark matter around a black hole can influence the inspiral of a second compact object and thus the gravitational waves emitted from such a binary. With the planned space-based gravitational-wave detector LISA, the distribution of dark matter on these small scales could be mapped precisely. This would provide a new method to study dark matter: with gravitational waves.

Over the years my group has performed a number of experiments realizing relativistic physics using cold atoms — described by the 1D Dirac Hamiltonian in some degree of approximation.  I will begin by reviewing these results in conjunction with those from the whole of the cold-atom community.

With that backdrop, I describe a spin dependent bipartite Floquet lattice, in which the dispersion relation is linear for all points in the Brillouin zone. The (stroboscopic) Floquet spectrum of our periodically-driven Hamiltonian features perfect spin-momentum locking, and a linear Dirac dispersion.  These bands are protected by a Floquet topological invariant which we directly measure by using quantum state tomography.

In recent years there has been much interest in the field of "analogue gravity", in which cosmological or astrophysical phenomena like Hawking radiation are mimicked in a laboratory experiment.  At LSU, my research group in cold atom/condensed matter theory became interested in this field, motivated by the recent experiment of Eckel and collaborators, [Phys. Rev. X 8, 021021 (2018)] who used a rapidly expanding Bose-Einstein condensate (BEC) to reproduce the inflationary regime of the early universe.  I will present our work on the physics of inflation in expanding BEC's, and discuss other setups to detect analogue gravity phenomena like the Unruh effect.  

With the milestone discovery of the Higgs boson at the CERN Large Hadron Collider (LHC), high energy physics has entered a new era. The completion of the “Standard Model” (SM) implies, for the first time ever, that we have a relativistic, quantum-mechanical, self-consistent theoretical framework, conceivably valid up to exponentially high energies, even to the Planck scale. Yet, the SM leaves many unanswered questions both from the theoretical and observational perspectives, including the nature of the electroweak superconductivity and its phase transition, the hierarchy between the particle masses and between the observed scales, the nature of dark matter etc. There are thus compelling reasons to believe that new physics beyond the SM exists. We argue that the collective efforts of future high energy physics programs, in particular the future colliders, hold great promise to uncover the laws of nature to a deeper level. 

Atomtronics is the emerging technology of building circuits where the current is a flow of ultracold atoms propagating as coherent matter waves inside suitable waveguides.  In this talk I will describe our atomtronic technology in which the waveguides are created with laser light via the optical dipole potential, and then discuss two quantum sensors based on it.  First, we have demonstrated the atomtronic analogue of the dc SQUID and shown that it exhibits the quantum interference that gives the Superconducting Quantum Interference Device its name.   In the conventional SQUID this is seen as a periodic variation of critical current with magnetic flux.  In the atomtronic SQUID it causes a periodic variation of critical current with rotation, enabling the device to function as a gyro.  Second, we are developing an atomtronic version of the Fiber Optic Gyro, in which rotation is measured by the Sagnac effect.  In our device a Bose-Einstein condensate is split, reflected, and recombined inside a waveguide that is translated so that the wavepackets travel around a loop and realize a waveguide Sagnac atom interferometer. 

Atom interferometers exploit spatially delocalized quantum states to make a wide variety of highly precise measurements.  Recent technological advances have opened a path for atom interferometers to contribute to multiple areas at the forefront of modern physics, including searches for wave-like dark matter, gravitational wave detection, and fundamental quantum science.  In this colloquium, I will describe MAGIS-100, a 100-meter-tall atom interferometer being built at Fermilab to pursue these directions.  MAGIS-100 will serve as a prototype gravitational wave detector in a new frequency range, between the peak sensitivities of LIGO and LISA, that is promising for pursuing cosmological signals from the early universe and for studying a broad range of astrophysical sources.  In addition, MAGIS-100 will search for wave-like dark matter, probe quantum mechanics in a new regime in which massive particles are delocalized over macroscopic scales in distance and time, and act as a testbed for advanced quantum sensing techniques.  Finally, I will discuss the potential and motivation for follow-on atomic detectors with even longer baselines.

The ongoing development of superconducting qubits has brought some basic questions of many-body physics to the research forefront, and helped solve several of them. I will address two effects in quantum condensed matter highlighted by the development of a fluxonium qubit. The first one is the so-called cosine-phi problem stemming from the seminal paper of Brian Josephson. It predicted the phase dependence of the dissipative current across the Josephson junction. A fluxonium qubit enabled the observation of the effect, after nearly 50 years of unsuccessful attempts by other techniques. The second one is inelastic scattering ("splitting") of a microwave photon by quantum fluctuations of phase across a Josephson junction. This effect is the elementary mechanism driving the Schmid transition, which predicts a collapse of the Josephson current in a junction influenced by a dissipative environment.

Marking the semi-anniversary of the Fermilab Muon g−2 experiment (E989) Run 1 result, this colloquium will review the current status of the muon magnetic anomaly, the inferred evidence of possible particles outside the Standard Model (SM), and future prospects in this active research field.

The intrinsic magnetic field of a simple object, such as a compass needle, is expressed in terms of its magnetic moment.  The magnetic moment of a point particle, such as the electron, is predicted by relativistic quantum mechanics to be g = 2, in convenient dimensionless units.  For the electron, this prediction fails at the part-per-thousand level; the resulting magnetic anomaly, a_e = (g − 2)/2, is due to the electron’s couplings to virtual particles excited in the vacuum.

Muon, the electron’s 200 times heavier cousin, experiences far stronger couplings to massive virtual particles, including possible non-SM exotics. The SM provides a prediction for the muon magnetic anomaly a_µ with sub-ppm precision. Hence, a comparably precise measurement of a_µ offers a uniquely sensitive test for the presence of non-SM particles in nature. For almost 20 years a tantalizing discrepancy of ∼ 3 – 4σ has persisted between the measurements of a_µ, and the SM calculations. The Fermilab Muon g−2 Run 1 result brings a much awaited update to this test, with much more to come.

Precision rotation sensing is useful for navigation, geophysics, and tests of fundamental physics. Atom interferometers provide, by some measures, the most sensitive method for rotation sensing achieved to date. However, the best performance requires freely falling atoms in a large experimental apparatus. Many applications, such as navigating a vehicle, will benefit from a more compact geometry. One method to achieve this is by using trapped atoms that are suspended against gravity. We have implemented such an interferometer and used it to measure a rotation rate comparable to that of the Earth. The most recent iteration of the interferometer has demonstrated improvements by a factor of ten in rotation sensitivity and trap stability. A second new apparatus reduces the scale of the vacuum chamber and optical system to roughly the size of a microwave oven.

Whereas the structure of the atom has been  understood for many years, the internal structure of the proton (and neutron) is the subject of active research.  Understanding the nucleon is difficult because its structure is governed by quantum chromodynamics, or QCD, which has not been solved exactly in the non-perturbative or low-energy regime.  The proton's structure is intriguing, however, for many reasons.  For example, we think of the proton as being made of three quarks, but the mass of those quarks only accounts for about 1% of the proton's mass.  The remaining 99%, and hence 99% of the known mass in the universe, is due to exotic effects associated with the QCD vacuum.  While a great deal of work remains to be done, the way in which we visualize the proton has changed dramatically since the discovery of quarks.  Just as the structure of the atom was unveiled early in the 20th century, the structure of the proton is being unveiled in the first decades of the 21st century.  Another intriguing aspect of the proton arises from the fact that QCD is the only theory in nature that has essentially no free parameters. String theory, that attempts to unify our understanding of gravity and the quantum world, grew out of early efforts to understand the strong interaction.  Since string theory deals with the topology of space and time, it is tempting to believe that a deep understanding of the proton may one day provide a window into even more fundamental questions. The colloquium will cover some recent developments in our understanding of the nucleon, as well as providing a glimpse of where this rich area of research is heading in upcoming years.

In quantum mechanics, the role of an observer is fundamentally different from that of a classical observer.  The quantum mechanical observer necessarily plays an active role in the dynamics of the system that it is observing.  This apparent difficulty may be turned into a tool to drive an initially trivial system into a complicated quantum many-body state simply by observing it.  I will present two remarkable examples of states induced by measurement. In the first, we examine the role of a moving density measuring device interacting with a system of fermions, and in particular, show that it would leave behind a wake of purely quantum origin. In the second example, inspired by the recent invention of topological Floquet insulators, we will see how a suitably chosen set of density measurements, repeated periodically, will induce robust chiral edge motion on a lattice of free fermions. Our examples show how quantum mechanical observation can be added as a versatile tool to the arsenal of quantum engineering in condensed matter systems.

The origin of complexity remains one of the most important and, at the same time, the most controversial scientific problems. Earlier attempts were based on theory of dynamical systems but did not lead to a satisfactory solution of the problem. I believe that a deeper understanding is possible based on a recent development of statistical physics, combining it with relevant ideas from evolutionary biology and machine learning.

Using patterns in magnetic materials as the main example, I discuss some general problems such as (a) a formal definition of pattern complexity [1]; (b) self-induced spin glassiness due to competing interactions as a way to interpret chaotic patterns [2]; (c) multi-well states intermediate between glasses and ordinary ordered states and their relevance for the problem of long-term memory in complicated systems [3]; and (d) complexity of frustrated quantum spin systems [4]. I will also review a very recent experimental observation of self-induced spin-glass state in elemental neodymium [5].

Geometrically frustrated many-body systems show many interesting emerging phenomena, ranging from kinetic frustration to exotic spin ordering and chiral spin liquid phases. Ultracold atom systems offer great tunability and flexibility to realize such systems in a wide parameter range of interactions, densities, and spin-imbalance.

In this talk, I will present our recent results on site-resolved imaging of ultracold fermionic lithium atoms on a triangular optical lattice.

Degenerate Fermi gases with about one tenth of the Fermi temperature have been realized within a crossed dipole trap and successfully loaded into a two-dimensional triangular optical lattice. To characterize this lattice, we observed Kapitza-Dirac scattering using a molecular Bose-Einstein condensate. Collecting the emitted photons during Raman sideband cooling in the triangular lattice using a high-resolution microscope objective enabled the high-fidelity imaging of individual fermionic atoms in the lattice with single-site resolution.

The next step will be the realization of a triangular lattice Hubbard model by implementing an additional optical lattice to increase interactions.

This novel experimental platform will allow us to study spin and density correlations in the triangular Hubbard model to explore signatures of frustration and spin-hole bound states and may lead to a direct observation of non-vanishing chiral correlations.

Bosonic modes are widely used for quantum communication and information processing. Recent developments in superconducting circuits enable us to control bosonic microwave cavity modes and implement arbitrary operations allowed by quantum mechanics, such as quantum error correction against excitation loss errors. We investigate different bosonic encoding and error correction protocols, and provide a perspective on using bosonic quantum error correction for various applications.

The unique properties of superfluid ⁴He (low mechanical stiffness, zero viscosity, high structural and chemical purity and extremely low optical loss) may allow the direct pursuit of optomechanics with quantum mechanical oscillators. We have constructed an optomechanical system consisting entirely of a magnetically levitated drop of superfluid ⁴He in vacuum. Levitation removes a source of loss associated with physically clamped oscillators. and allows the drop to efficiently cool itself via evaporation. The drop’s optical whispering gallery modes (WGMs) and its surface vibrations couple to each other via the usual optomechanical interactions. We demonstrate the stable magnetic levitation of superfluid ⁴He drops in vacuum, and present measurements of the drops' evaporation rates, temperatures, optical modes and surface vibrations. We found optical modes with finesse ≈40 (limited by the drop's size). We found surface vibrations with decay rates ∼1 Hz (in rough agreement with theory). Lastly, we found that the drops reach a temperature T≈330 mK, and that a single drop can be trapped indefinitely.

The full potential of the Large Hadron Collider will ultimately be realized through the running period that will take collider operations into the late 2030s. The so-called High Luminosity era of the LHC (HL-LHC), planned to begin in 2027, will see up to a 5-fold increase in the nominal brightness of the LHC beams, which will consequently allow experiments to collect a data set of proton-proton collisions approximately 20 times larger than what has been collected so far in high-energy LHC running. This significant increase in data sample will be a boon for the physics program of the LHC experiments, furthering searches for ultra-rare phenomena and refining precision measurements of known processes. At the CMS experiment, a suite of novel upgrades will be deployed that will enable the experiment to cope with the onslaught of collisions in the high luminosity environment and fully capitalize on the opportunities presented in the HL-LHC era. In this talk I will focus on the MIP Timing Detector (MTD), a device capable of measuring the time-of-arrival for minimum-ionizing particles (MIPs) produced within CMS with a resolution of 30 picoseconds. This entirely new detector system will be built in part at UVA before being shipped to CERN and integrated with the CMS experiment. I will describe the principle of operation of the MTD, the current status of the project and UVA's role in the construction of the device. I will also discuss the expected impact the MTD will have on several high-profile physics signatures that are prime targets in the HL-LHC era and, in particular, the power of using timing information in the reconstruction of exotic long-lived particle decays. 

In this talk, I will present our recent efforts on dynamical simulations of correlated electron systems. I will first discuss new quantum molecular dynamics (QMD) methods based on advanced many-body techniques, such as Gutzwiller/slave-boson and dynamical mean-field theory, that are capable of modeling strong electron correlation phenomena. We apply our new QMD to simulate the correlation-induced Mott transition in a metallic liquid, and the nucleation-and-growth of Mott droplets in Hubbard-type models. I will also discuss the implementation of the ab initio Gutzwiller MD for simulating hydrogen liquids under high pressure. To overcome the obstacle of huge computational complexity in such large-scale simulations, I will discuss how simulation efficiency can be significantly improved with the aid of modern machine learning methods. In particular, deep-learning neural-network holds the potential of achieving large-scale quantum-accuracy simulation of correlated systems without the electrons.

‘Circuit QED’ is the quantum theory of superconducting qubits strongly interacting with microwave photons in electrical circuits. It is the leading solid-state architecture in the race to develop large-scale fault-tolerant quantum computers, and is the only technology that has demonstrated quantum error correction that actually extends the lifetime of quantum information. 

In this talk, I will present an elementary introduction to the basic concepts underlying superconducting quantum processors. Their ability to control and make quantum non-demolition (QND) measurements of individual microwave photons is a powerful resource for quantum computation, communication and simulation.   I will illustrate these capabilities with recent experiments on a programmable quantum simulator that uses efficient boson sampling of microwave photons to predict the Franck-Condon vibrational spectra of various small tri-atomic molecules.  Finally, I will briefly explore possible future directions for simulation of quantum many-body problems involving interacting bosons.

The ability to generate and manipulate photons with high efficiency and coherence is of critical importance for both fundamental quantum optics studies and practical device applications. However mainstream integrated photonic platforms such as those based on silicon and silicon nitride lack the preferred cubic c(2) nonlinearity, which limits active photon control functionalities. In this talk, I will present integrated photonics based on aluminum nitride (AlN) and lithium niobite (LN), whose non-centrosymmetric crystal structures give rise to the strong second-order optical nonlinearity. Together with their low optical loss, the integrated AlN and LN photonics can provide enhanced c(2) photon-photon interactions to achieve high fidelity photon control, including on-chip parametric down-conversion, coherent light conversion, spectral-temporal shaping, and microwave-to-optical frequency conversions.

The general lore, according to effective field theory, is that one ignores the high energy degrees of freedom when studying low energy phenomena. For example, we usually do not need to know quantum chromodynamics (QCD) (the strong nuclear force) in order to study fluid mechanics! However, the existence of 't Hooft anomalies (subtle phases in the partition function) may signal non-trivial intertwining between the high and low energy scales. This assertion can be seen in axion physics; axion is a hypothetical particle that may play important roles in solving a few puzzles in the Universe.  After a brief introduction to QCD and axions, I show how this intertwining takes place on axion domain walls (DW). To this end, I first discuss a new class of 't Hooft anomalies that was recently identified, and then use the anomalies to argue that quarks are deconfined (liberated) on axion DW. This newly discovered phenomenon implies that non-trivial interplay between different scales happens on the walls. Further, I confirm this picture by performing explicit calculations in a toy model, which is argued to be continuously connected to the full-fledged QCD.

Quantum field theory is a universal language in theoretical physics, which provides the foundation for the Standard Model of elementary particles, underlies the physics of the early universe, and describes a wealth of interesting phenomena in condensed matter. But despite its great successes, fully understanding this important framework is still very much a work in progress. Many insights, especially into theories with strong interactions, have been obtained using mathematical tools from string theory, and this has reshaped our understanding of what quantum field theory is. In this talk I will discuss new connections between quantum field theory and string theory that provide access to a remarkable class of theories that would not have been believed to exist based on conventional lore.

Neutrinos are the most elusive known elementary particles; they fly through all of us in vast numbers but are extremely difficult to detect. Immense progress has been made in analyzing their properties over the last decades, culminating in the surprising discovery of neutrino flavor oscillations. These neutrino oscillations imply that neutrinos have tiny but nonzero masses, which provides strong evidence for physics beyond the Standard Model of particle physics. With the increasing precision in neutrino measurements it has even become possible to use neutrinos as a tool to probe for further new physics, e.g. by studying how neutrinos scatter off electrons. In addition, neutrinos could prove uniquely helpful in the search for dark matter and provide complementary information to standard indirect detection signatures.

I will address two of the most fundamental questions about our Universe -- "What is the Universe made of?” and "How did complex structures come to exist?”. These translate into understanding the origins of dark matter and a mechanism to generate the asymmetry of matter over anti-matter in the early Universe. I will put these problems in context and then present a novel, testable, solution to both mysteries in the same framework.  The key idea is to rely on Standard Model particles called Beauty (B) Mesons which decay into dark matter particles. This mechanism has multiple testable signals. Some experimental searches are already under development, the results of which could yield the first hints of how nature chose to address these profound questions.

A hundred years after the prediction by Einstein, gravitational waves were directly detected for the first time in 2015 by LIGO, which marked the dawn of gravitational-wave astronomy. Gravitational waves are sourced by astrophysical compact objects, such as black holes and neutron stars. Due to their extremely large gravitational field and compactness, they offer us natural testbeds to probe strong-field gravity and dense matter physics. In this talk, I first give an overview of the current status of gravitational-wave observations. Next, I explain how well one can test General Relativity, constrain the equation of state of nuclear matter and measure nuclear parameters with gravitational waves. I also comment on how one can combine gravitational-wave information with the recent measurement of a neutron star radius by an X-ray payload NICER to further probe nuclear physics.

When learning about the properties of a quantum mechanical system, for instance, the energy levels of its bound states, it is useful to think of the system as closed and isolated from any environment, though we know in any laboratory setting, all systems eventually will interact with an environment. However, we can often engineer such interactions to be weak, short-ranged, and controllable, so that the isolated approximation is a good one.

I will argue that in many physically relevant field theories, the long-time observables or states of the theory can only be defined in the context of a quantum open system, where we take into account the interactions between the system and the environment continually in the evolution of the system. This is because excitations of the field theory will inevitably create their own environment, that is, states we must trace over. Resumming these interactions with the self-created environment is necessary to give a convergent expansion for observables over all of phase-space.

Microscopic quantum interactions between elementary particles control transport in macroscopic states of matter, such as in fluids and plasmas. In numerous states of interest, these microscopic interactions are strong, including in water, among electrons in graphene and in quark-gluon plasma — a state of nuclear matter that filled the early Universe and that is currently being recreated in particle colliders. While macroscopic theories describing the dynamics of such states, in particular, hydrodynamics (of fluids) and magnetohydrodynamics (of magnetized plasmas) have been partially understood, a full description of transport also requires a certain microscopic knowledge of its underlying quantum physics. After more than a century of striking advance in quantum theories, our theoretical understanding of these microscopic processes remains mostly limited to states with weak interactions. Recently, however, string theory also enabled explorations of strongly interacting states through the mathematical statement of holographic duality, which translates otherwise intractable problems into simpler analyses of black holes and gravitational waves.   

In my talk, I will first discuss new aspects of the macroscopic theory of hydrodynamics, focusing on the properties of the infinite series of higher-order corrections to the infamous Navier-Stokes equations. By using a novel concept of generalized global symmetries, which can encode the fact that the number of magnetic flux lines in Nature is conserved, I will then describe the construction of a new, comprehensive theory of magnetohydrodynamics. This reformulation has led to a number of general theoretical and experimental predictions for transport in magnetized plasmas. I will then move on to discuss the microscopic physics responsible for transport in strongly interacting states. Beginning with an introduction of holographic duality, this section will summarize holographic insights into the problem of the “unreasonable effectiveness of hydrodynamics” for the description of quark-gluon plasma. Then, I will discuss how the descriptions of microscopic physics and transport transition between strongly and weakly interacting pictures. Finally, by utilizing the mathematical structure behind our new theory of magnetohydrodynamics, a holographic dual of magnetized plasmas will be presented along with the first analyses of strongly interacting magnetized transport.

Direct experimental evidence for point-like constituents in the nucleons
was first found in the electron deep inelastic scattering (DIS) experiment.
The discovery of the valence and sea quark structures in the nucleons
inspired the formulation of Quantum Chromodynamics (QCD) as the gauge field
theory governing the strong interaction. A surprisingly large asymmetry
between the up and down sea quark distributions in the nucleon was observed
in DIS and the so-called Drell-Yan experiments. In this talk, I discuss the
current status of our knowledge on the flavor structure of the nucleon sea.
I will also discuss the progress in identifying the "intrinsic" sea
components in the nucleons. Future prospect for detecting some novel
sea-quark distributions will also be presented.

We live in an exciting era where strong-field gravity has become a central pillar in the study of astrophysical sources.   For the first time in history the detection of gravitational waves and simultaneous electromagnetic signals (multimessenger astronomy) from the same source have the potential to solve some of the most long-standing problems in fundamental physics and astrophysics. Computational gravity plays an important role in the success of the multimessenger astronomy program. Using the vantage point of computational gravity, in this talk we will we focus on how observations of colliding neutron stars can teach us about the state of matter at densities greater than the nuclear density, and with a critical eye assess what we have learnt so far from the first observation of a binary neutron star (event GW170817). We will also discuss how multimessenger detection of collisions of binary black holes may inform us about their environments andthe nature of black holes.

Advanced LIGO and Virgo have already detected black holes crashing into each other at least ten times. With their upgrades we anticipate a rate of about 1 gravitational-wave detection per week. More signals and higher precision will take the dream of testing Einstein's theory of gravity, general relativity, and make it a reality. But would we know a correction to Einstein's theory if we saw it? How do we make predictions from theories beyond GR? And do current numerical relativity simulations have enough precision that we could be confident in any potential discrepancy between observations and predictions? I will discuss (i) how to perform simulations in beyond-GR theories of gravity, and (ii) how numerical relativity simulations need to improve to be ready for the precision frontier of gravitational wave astrophysics.

Heavy-ion collisions can produce nuclear material over a range of densities and proton fractions to study the nuclear equation-of-state. These measurements are enabled by accelerating nuclei to – in some cases – GeV energies and detecting the fragments that are produced from the collisions.  The detectors are multi-detector arrays capable of measuring dozens of particles simultaneously from a single collision.  Data rates can range up to many hundreds of collisions per second. One can either explore the characteristics of the individual fragments that are produced, often extracting particle ratios or double ratios, or correlations between the fragments – in particular transverse collective flow.  From very low density to about three times normal nuclear density measurements have been made of the density dependence of the asymmetry energy.  I will present an overview of how these measurements have been made and the constraints they have set on the nuclear equation-of-state.

We are in the midst of a second quantum revolution fueled by “quantumness” of physical systems and the sophisticated measurement devices or detectors to produce and characterize these exotic systems. Thus, characterization of quantum states and the detectors is a key task in optical quantum science and technology. The Wigner quasi-probability distribution function provides such a characterization. In this talk, I present our recent results on quantum state tomography of a single-photon Fock state using photon-number-resolving measurements using superconducting transition-edge sensor [1]. We directly probe the negativity of the Wigner function in our raw data without any inference or correction for decoherence, which is also an important indicator of the “quantum-only” nature of a physical system. For the second part of the talk, we discuss a method to characterize quantum detectors by experimentally identifying the Wigner functions of the detector positive-operator-value-measures (POVMs), a set of hermitian operators completely describing the detector [2]. The proposed scheme uses readily available thermal mixtures and probes the Wigner function point-by-point over the entire phase space from the detector’s outcome statistics. In order to make the reconstruction robust to the experimental noise, we use techniques from convex quadratic optimizations.

References
1. R. Nehra, A. Win, M. Eaton, R. Shahrokhshahi, N. Sridhar, T. Gerrits,A. Lita, S. W. Nam, and O. Pfister, “State-independent quantum state tomography by photon-number-resolving measurements,” Optica 6,1356–1360 (2019). 2. R. Nehra and K. Valson Jacob (2019), “Characterizing quantum detectors by Wigner functions,” [arXiv:1909.10628].
 

Lead halide perovskites have been demonstrated as high performance materials in solar cells and light-emitting devices. These materials are characterized by coherent band transport expected from crystalline semiconductors, but dielectric responses and phonon dynamics typical of liquids.  Here we explain the essential physics in this class of materials based on their dielectric functions and dynamic symmetry breaking on nano scales. We show that the dielectric function in the THz region may lead to dynamic and local ordering of polar nano domains by an extra electron or hole, resulting a quasiparticle which we call a ferroelectric large polaron, a concept similar to solvation in chemistry. Compared to a conventional large polaron, the collective nature of polarization in a ferroelectric large polaron may give rise to order(s)-of-magnitude larger reduction in the Coulomb potential. We show that the shape of a ferroelectric polaron resemble that of a Belgian waffle. Using two-dimensional coherent phonon spectroscopy, we directly probe the energetics and local phonon responses of the ferroelectric large polarons. We find that that electric field from a nascent e-h pair drives the local transition to a hidden ferroelectric order on picosecond time scale.  The ferroelectric or Belgian waffle polarons may explain the defect tolerance and low recombination rates of charge carriers in lead halide perovskites, as well as providing a design principle of the “perfect” semiconductor for optoelectronics.

A major challenge of physics is the complexity of many-body systems. While true for classical systems, the difficulty is exasperated in quantum systems, due to entanglement between system components and thus the need to keep track of an exponentially large number of parameters. In particular, this complexity places a challenge to numerical methods such as quantum Monte Carlo and tensor networks. Here, exactly solvable models are of crucial importance:  we use these to test numerical procedures, to develop intuition, and as a starting point for approximations.

In this talk, I will explain our current understanding of a new solvable "walk" model, the area deformed Motzkin model. The model shows that entanglement may be more acute than previously thought, in particular, it features a novel quantum phase transition between a non-entangled phase and extensively entangled “rainbow” phase. Most remarkably, the model motivated the construction of a new tensor network, providing, after many years, the first example for an exact tensor network description of a critical system. Finally, I will remark on open problems, and on exciting connections to other fields such as the notion of holography in field theory, and a famous problem in non-equilibrium statistical mechanics.

Neutron stars are one of the densest strongly-interacting many-body systems in our universe. A main challenge in describing the structure and dynamics of neutron stars steams from our limited understanding of the nuclear interaction at high-densities (i.e. short-distances) and its relation to the underlaying quark-gluon substructure of nuclei.

In this talk I will present new results from high-energy electron scattering experiments that probe the short-ranged part of the nuclear interaction via the hard breakup of Short-Range Correlations (SRC) nucleon pairs. As the latter reach densities comparable to those existing in the outer core of neutron stars, they represent ’neutron stars droplets’ who’s study can shed new light to the dynamical structure of neutron stars. Special emphasis will be given to the effect of SRCs to the behavior of protons in neutron-rich nuclear systems and how it can impact the cooling rates and equation of state of neutron stars.  Pursuing a more fundamental understanding of such interactions, I will present new measurements of the internal quark-gluon sub-structure of nucleons and show how its modification in the nuclear medium relates to SRC pairs and short-ranged nuclear interactions. 

Given time I will also discuss the development of new effective theories for describing short-ranged correlations, the way in which they relate to experimental observables, and the emerging universality of short-distance and high-momentum physics in nuclear systems.

Ising anyons, Majorana fermions (MF) and zero energy Majorana bound states have promising prospects in topological quantum computing (TQC) because of their ability to store quantum states non-locally in space and insensitivity to local decoherence. Unfortunately, these objects are not powerful enough to assemble a TQC that can perform universal operations using topological braiding operations alone. On the other hand, there are anyonic quasiparticles, like the Fibonacci anyon in a Read-Rezayi quantum Hall state, that are universal in the braiding-based TQC sense. However, these are quantum dynamical excitations, which can be challenging to spatially manipulate and susceptible to temperature fluctuations in a thermodynamic system. We propose and define a new notion of universal fractional quasiparticles, which are semi-classical static topological defects, supported by many-body interacting MFs in a superconducting spin-orbit coupled topological electronic system.

Of course, multimessenger astronomy promises to revolutionize

astronomy and our understanding of nucleosynthesis. My

research shows that it goes further: astronomical observations

(via both photons and gravitational waves) provides a unique

laboratory to deepen our understanding of QCD and the

nucleon-nucleon interaction. Most current work is focused

on the equation of state. While the equation of state is

indeed important, in this talk, I show how we can

go beyond energy density and pressure. I present the first

large-scale Bayesian inference of neutron star observations

and nuclear structure data to obtain novel results on the

composition of dense matter and the nature of nucleonic

superfluidity.

Quantum Chromodynamics (QCD), the nuclear physics part of the Standard Model, is the first theory to demand that science fully resolve the conflicts generated by joining relativity and quantum mechanics.  Hence in attempting to match QCD with Nature, it is necessary to confront the innumerable complexities of strong, nonlinear dynamics in relativistic quantum field theory.  The peculiarities of QCD ensure that it is also the only known fundamental theory with the capacity to sustain massless elementary degrees-of-freedom, gluons (gauge bosons) and quarks (matter fields); and yet gluons and quarks are predicted to acquire mass dynamically so that the only massless systems in QCD are its composite Nambu-Goldstone bosons.  All other everyday bound states possess nuclear-size masses, far in excess of anything that can directly be tied to the Higgs boson.  These points highlight the most important unsolved questions within the Standard Model, namely: what is the source of the mass for the vast bulk of visible matter in the Universe and how is this mass distributed within hadrons?  This presentation will provide a contemporary sketch of the strong-QCD landscape and insights that may help in answering these questions.

In conventional imaging systems, the results are poor unless there is a physical mechanism for producing a sharp image with high signal-to-noise ratio.  In this talk, I will present two settings where computational methods enable imaging from very weak signals:  range imaging and non-line-of-sight (NLOS) imaging.

Lidar systems use single-photon detectors to enable long-range reflectivity and depth imaging.  By exploiting an inhomogeneous Poisson process observation model and the typical structure of natural scenes, first-photon imaging demonstrates the possibility of accurate lidar with only 1 detected photon per pixel, where half of the detections are due to (uninformative) ambient light.  I will explain the simple ideas behind first-photon imaging and lightly touch upon related subsequent works that mitigate the limitations of detector arrays, withstand 25-times more ambient light, allow for unknown ambient light levels, and capture multiple depths per pixel.

NLOS imaging has been an active research area for almost a decade, and remarkable results have been achieved with pulsed lasers and single-photon detectors.  Our work shows that NLOS imaging is possible using only an ordinary digital camera.  When light reaches a matte wall, it is scattered in all directions.  Thus, to use a matte wall as if it were a mirror requires some mechanism for regaining the one-to-one spatial correspondences lost from the scattering.  Our method is based on the separation of light paths created by occlusions and results in relatively simple computational algorithms.

Related paper DOIs:
10.1126/science.1246775
10.1109/TSP.2015.2453093
10.1109/LSP.2015.2475274
10.1364/OE.24.001873
10.1038/ncomms12046
10.1109/TSP.2017.2706028
10.1038/s41586-018-0868-6

Complex oxides are known to possess the full spectrum of fascinating properties, including magnetism, colossal magneto-resistance, superconductivity, ferroelectricity, pyroelectricity, piezoelectricity, multiferroicity, ionic conductivity, and more. This breadth of remarkable properties is the consequence of strong coupling between charge, spin, orbital, and lattice symmetry. Spurred by recent advances in the synthesis of such artificial materials at the atomic scale, the physics of oxide heterostructures containing atomically smooth layers of such correlated electron materials with abrupt interfaces is a rapidly growing area. Thus, we have established a growth technique to control complex oxides at the level of unit cell thickness by pulsed laser epitaxy. The atomic-scale growth control enables to assemble the building blocks to a functional system in a programmable manner, yielding many intriguing physical properties that cannot be found in bulk counterparts. In this talk, examples of artificially designed, functional oxide heterostructures will be presented, highlighting the importance of heterostructuring, interfacing, and straining. The main topics include (1) charge transfer induced interfacial magnetism and topologically non-trivial spin textures in SrIrO₃-based heterostructures and (2) lattice and chemical potential control of oxygen stability and associated electronic and magnetic properties in nickelate-and cobaltite-based heterostructures.

This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

This presentation describes an arc in mathematical/theoretical physics traversing concepts from equations, graphs, error-correction, and pointing toward an evolution-like process acting on the  mathematical laws that sustain reality.

Water wave patterns behind ships fuel human curiosity because they are both beautiful and easily observed.  These patterns called wakes were famously described in 1887 by Lord Kelvin.  According to Kelvin, the feather-like appearance of the wake is universal and the entire wake is confined within a 39 degree angle.  While such wakes have been observed, deviations from Kelvin’s predictions have also been reported.  In this talk summarizing my work with UVA alumnus Jonathan Colen I will present a quantitative reasoning based on classical surface water wave theory that explains why some wakes are similar to Kelvin’s prediction, and why others are less so.  The central result is a classification of wake patterns which all can be understood in terms of the problem originally treated by Kelvin.

Gravitational waves from the mergers of ten binary black holes and one binary neutron star were detected in the first two observing runs by the Advanced LIGO and Virgo detectors. In this talk, I will discuss the eleven gravitational-wave detections and the electromagnetic observations that accompanied the neutron-star merger. These detections confirmed many of the predictions of general relativity, and they initiated the observational study of strongly curved, dynamical spacetimes and their highly luminous gravitational waves. One aspect of these high gravitational-wave luminosities that LIGO and Virgo will be able to measure is the gravitational-wave memory effect: a lasting change in the gravitational-wave strain produced by energy radiated in gravitational waves. I will describe how this effect is related to symmetries and conserved quantities of spacetime, how the memory effect can be measured with LIGO and Virgo, and how new types of memory effects have been recently predicted. I will conclude by discussing the plans for the next generation of gravitational-wave detectors after LIGO and Virgo and the scientific capabilities of these new detectors. These facilities could detect millions of black-hole and neutron-star mergers per year, and they can provide insights on a range of topics from the population of short gamma-ray bursts to the presence of dark matter around black holes.

The next decade promises fundamental new scientific insights and discoveries from Multi-Messenger Astrophysics, enabled through the convergence of large scale astronomical surveys, gravitational wave astrophysics, deep learning and large scale computing. In this talk I describe a Multi-Messenger Astrophysics science program, and highlight recent accomplishments at the interface of gravitational wave astrophysics, numerical relativity and deep learning. I discuss the convergence of this program with large scale astronomical surveys in the context of gravitational wave cosmology. Future research and development activities are discussed, including a vision to leverage data science initiatives at the University of Virginia to spearhead, maximize and accelerate discovery in the nascent field of Multi-Messenger Astrophysics.

 

Black holes are bridges between astrophysics and fundamental physics.  I will describe three examples of this theme.  First, I will explain how contemporary theoretical ideas deriving from the holographic principle have proven useful for interpreting numerical simulations of electromagnetic outflows from spinning black holes.  These models are currently being tested against X-ray and radio observations of galactic black holes.  Second, I will describe a correspondence between black holes and lower dimensional fluids and discuss the possibility of probing this correspondence with gravitational wave memory experiments.  Finally, I will describe how gravitational wave observations of black hole tidal interactions might be used to find new symmetries acting on the event horizon.

We are entering a golden age of cosmology and astrophysics. In the coming decade we will have cosmological data for over a billion galaxies, a census of objects in the Milky Way, and a network of gravitational detectors spanning the globe that will detect thousands of events per year. This presents us with the unprecedented opportunity to learn how gravity behaves at the largest distances, and in the most extreme environments. In this talk I will describe how we can use current and upcoming data to understand the unexplained mysteries of the Universe, such as why the expansion of the Universe accelerating (dark energy). I will also discuss how to connect physics in these disparate regimes and how to test cosmology on small scales. To maximize the discovery potential of the data requires us to construct robust theoretical models, identify novel probes, and connect theory with observation, and I will describe projects where I have attempted to accomplish this. I will conclude the talk by discussing how this interdisciplinary effort will continue into the next decade and beyond.    

 

Observations have shown that nearly all galaxies harbor massive or supermassive black holes at their centers. Gravitational wave (GW) observations of these black holes will shed light on their growth and evolution, and the merger histories of galaxies. Massive and supermassive black holes are also ideal laboratories for studying strong-field gravity. Pulsar timing arrays (PTAs) are sensitive to GWs with frequencies ~1-100 nHz, and can detect GWs emitted by supermassive black hole binaries, which form when two galaxies merge. The Laser Interferometer Space Antenna (LISA) is a planned space-based GW detector that will be sensitive to GWs ~1-100 mHz, and it will see a variety of sources, including merging massive black hole binaries and extreme mass-ratio inspires (EMRIs), which consist of a small compact object falling into a massive black hole. I will discuss source modeling and detection techniques for LISA and PTAs, as well as present limits on nanohertz GWs from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration.

Quantum Chromodynamics (QCD), the theory of the strong interaction, is a cornerstone of the Standard Model of modern physics. It explains all nuclear matter as bound states of point-like fermions, known as quarks, and gauge bosons, known as gluons. The gluons bind not only quarks but also interact with themselves. Unlike with the more familiar atomic and molecular matter, the interactions and structures are inextricably mixed up, and the observed properties of nucleons and nuclei, such as mass and spin, emerge out of this complex system. To precisely image the quarks and gluons and their interactions and to explore the new QCD frontier of strong color fields in nuclei, the Nuclear Physics community proposes an US-based Electron Ion collider (EIC) with high-energy and high-luminosity, capable of a versatile range of beam energies, polarizations, and ion species. The community is convinced that the EIC is the right tool to understand how matter at its most fundamental level is made.

A global quantum revolution is currently underway based on the recognition that the subtler aspects of quantum physics known as superposition (wave-like aspect), measurement (particle-like aspect), and entanglement (inseparable link between the two aspects) are far from being merely intriguing curiosities, but can be transitioned into valuable, real-world technologies with performances that can far exceed those obtainable with classical technologies. The recent demonstration by the Chinese scientists of using a low-earth-orbit satellite to distribute entangled photons to two ground stations that are over a thousand kilometers apart is a stunning technological achievement—direct entanglement distribution over the best available fiber links is limited to a few hundred kilometers—and a harbinger of future possibilities for globally secure communications guaranteed by the power of quantum physics.

Harnessing the advantages enabled by superposition, measurement, and entanglement (SME)—the three pillars of quantum physics—for any given application is what is termed quantum engineering in general. In many instances, however, the details of the underlying science (high-temperature superconductivity, photosynthesis, avian navigation, are some examples) is still not fully understood, let alone how to turn the partially understood science into a potentially useful technology. Nevertheless, it has become clear in the last few decades that quantum engineering will require a truly concerted effort that will need to transcend the traditional disciplinary silos in order to create and sustain new breeds of science and technology communities that will be equally versed in quantum physics as they would be in their chosen area of technology. In this talk, I will present my vision for unleashing the potential of quantum engineering, taking some examples from ongoing and proposed research.

The bounty of gravitational-wave observations from LIGO and Virgo has opened up a new window onto the warped Universe, as well as a pathway to addressing many of the contemporary challenges of fundamental physics. I will discuss how catalogs of stellar-mass compact object mergers can probe the unknown physical processes of binary stellar evolution, and how these systems can be harnessed as standard distance markers (calibrated entirely by fundamental physics) to map the expansion history of the cosmos. The next gravitational-wave frontier will be opened within 3-6 years by pulsar-timing arrays, which have unique access to black-holes at the billion to ten-billion solar mass scale. The accretionary dynamics of supermassive black-hole binaries should yield several tell-tale signatures observable in upcoming synoptic time-domain surveys, as well as gravitational-wave signatures measurable by pulsar timing. Additionally, pulsar-timing arrays are currently placing compelling constraints on modified gravity theories, cosmic strings, and ultralight scalar-field dark matter. I will review my work on these challenges, as well as in the exciting broader arena of gravitational-wave astrophysics, and describe my vision for the next decade of discovery. 

I will begin by describing an interacting model in Quantum Mechanics where exact results about the ground state can be established by using tools from topology. I will then argue that such tools are also useful for tackling interesting problems in Quantum Field Theory. In particular, I will review Yang-Mills theory and argue that using topology one can make several predictions about its possible phases. We will then also extend the considerations to Quantum Chromodynamics and discuss possible connections with particle physics phenomenology and with condensed matter physics.

“An observation of neutron-antineutron oscillations (n-n ̅), which violate both B and B — L conservation, would constitute a scientific discovery of fundamental importance to physics and cosmology. A stringent upper bound on its transition rate would make an important contribution to our understanding of the baryon asymmetry of the universe by eliminating the post-sphaleron baryogenesis scenario in the light quark sector. We show that one can design an experiment using slow neutrons that in principle can reach the required sensitivity of 10¹⁰ s in the oscillation time, an improvement of 10⁴ in the oscillation probability relative to the existing limit for free neutrons. This can be achieved by allowing both the neutron and antineutron components of the developing superposition state to coherently reflect from mirrors. We present a quantitative analysis of this scenario and show that, for sufficiently small transverse momenta of n/n ̅ and for certain choices of nuclei for the n/n ̅ guide material, the relative phase shift of the n and n ̅ components upon reflection and the n ̅ annihilation rate can be small. While the reflection of n ̅ from surface looks exotic and counterintuitive and seems to contradict to the common sense, in fact it is fully analogous to the reflection of n from surface. The later phenomenon is well known and used in neutron research from its first years. We illustrate it with two selected example of gravitational and whispering-gallery quantum states of neutrons.”

[V.V. Nesvizhevsky, A.Yu. Voronin, Surprising Quantum Bounces, Imperial College Press, London, 2015]  

Human brains can solve many problems with orders of magnitude more energy efficiency than traditional computers.  As the importance of such problems, like image, voice, and video recognition, increases, so does the drive to develop computers that approach the energy efficiency of the brain.  Magnetic devices, especially tunnel junctions, have several properties that make them attractive for such applications.  Their conductance depends on the state of the ferromagnets making it easy to read information that is stored in their magnetic state.  In addition, current can manipulate the magnetic state.  Based on this electrical control of the magnetic state, magnetic tunnel junctions are actively being developed for integration into CMOS integrated circuits to provide non-volatile memory.  This development makes it feasible to consider other geometries that have different properties.  I describe two of the computing primitives that have been constructed based on the different functionalities of magnetic tunnel junctions.  The first of these uses tunnel junctions in their superparamagnetic state as the basis for a population coding scheme.  The second uses them as non-linear oscillators in the first nanoscale “reservoir” for reservoir computing.

Most of my talk will be about anomalous thermal relaxations, such as the Mpemba effect. Towards the end of my talk, I will also highlight a few topics in population dynamics that I have been working on. 

The Mpemba effect is a phenomenon when "hot can cool faster than cold" - a “shortcut” in relaxation to thermal equilibrium. It occurs when a physical system initially prepared at a hot temperature, cools down faster than an identical system prepared at a colder temperature. The effect was discovered as a peculiarity of water. Despite following observations in granular gasses, magnetic alloys, and spin glasses, the effect is still most often referred to as an “oddity” of water, although it is widespread and general.  I will describe how to define a Mpemba effect for an arbitrary physical system, and show how to quantify and estimate the probability of the Mpemba effect on a few examples. 

In the remaining time, I will briefly talk about the adaptation of bacterial populations and the immune system of bacteria with CRISPR.  Besides being the biology's newest buzzword and favorite gene editing tool, CRISPR is also a mechanism that allows bacteria to defend adaptively against phages and other invading genomic material. From the standpoint of physics and biology, the coevolution of bacteria and phages yields fascinating open questions. 

The steady increase in computational power of information processors over the past half-century has led to smart phones and the internet, changing commerce and our social lives.  Up to now, the primary way that computational power has increased is that the electronic components have been made smaller and smaller, but within the next decade feature sizes are expected to reach the fundamental limits imposed by the size of atoms.  However, it is possible that further huge increases in computational power could be achieved by building quantum computers, which exploit in new ways of the laws of quantum mechanics that govern the physical world.  This talk will discuss the challenges involved in building a large-scale quantum computer as well as progress that we have made in developing a quantum computer using silicon quantum dots.  Prospects for further development will also be discussed.

Many unusual properties of strongly correlated materials have been attributed to the proximity of quantum phase transitions (QPTs), where different types of orders compete and coexist, and may even give rise to novel phases.  In two-dimensional (2D) systems, the nature of the magnetic-field-tuned QPT from a superconducting to a normal state has been widely studied, but it remains an open question.  Underdoped copper-oxide high-temperature superconductors are effectively 2D materials and thus present a promising new platform for exploring this long-standing problem.  Although in cuprates the normal state is commonly probed by applying a perpendicular magnetic field (H) to suppress superconductivity, the identification and understanding of the H-induced normal state has been a challenge because of the complex interplay of disorder, temperature and quantum fluctuations, and the near-universal existence of charge-density-wave correlations. 

This talk will describe recent experimental advances in identifying and characterizing a full sequence of ground states as a function of H in underdoped cuprates.  In both the absence and the presence of charge order, the results demonstrate the key role of disorder in the H-tuned suppression of 2D superconductivity, giving rise to an intermediate regime with large quantum phase fluctuations, in contrast to the conventional scenario.  Most strikingly, the interplay of the “striped” charge order with high-temperature superconductivity leads to the emergence of an unanticipated, insulatinglike ground state with strong superconducting phase fluctuations, suggesting an unprecedented freezing (i.e. “the hidden order”) of Cooper pairs.  Possible scenarios will be discussed, including the implications of the results for understanding the physics of the cuprate pseudogap regime, as well as other 2D superconductors.

Layered transition-metal dichalcogenides (TMDs) are well known for their rich phase diagrams, which
encompass diverse quantum states including metals, semiconductors, Mott insulators, superconductors, and
charge density waves (CDWs). For instance, 2H-NbSe₂ and 2H-TaS₂ are canonical incommensurate CDW
systems, while 1T-TiSe₂ harbors a commensurate CDW order. There is a coexistence/competition of CDW
and superconductivity in 2H-NbSe₂ and 2H-TaS₂, though this is not the case for pristine 1T-TiSe₂. A subtle
interplay of CDW and superconducting orders, however, appears in each of these materials via chemical
intercalation or under pressure. Such a competition between or coexistence of proximate broken-symmetry
phases resembles many aspects of the phase diagram of cuprate high temperature superconductors
(HTSCs)—particularly, in the underdoped regime where the enigmatic pseudogap phase exists. The origin
of the CDW order in these compounds is an intriguing puzzle despite decades of research. We will present
our experimental data, which combine Angle Resolved Photoemission Spectroscopy, Scanning Tunneling
Spectroscopy, scattering and transport measurements, to provide new insights into the relative importance
of lattice and Coulomb effects in the CDW transitions of these compounds. These studies will also highlight
the distinctive impacts of disorder and doping in commensurate and incommensurate CDW systems.
Finally, comparing spectroscopic features of the CDW state of the TMDs with those of the normal state
underdoped HTSCs, we will discuss whether a CDW order can possibly be the origin of the pseudogap
phase in the cuprates.

2018 is the 100th Anniversary of the birth of Richard Feynman.
His discoveries and new formalisms, and the way he thought about
solving problems, transformed the way we think
about physics. I will talk about examples of how these impacted present results
in nuclear and particle physics.

I will also expand upon what might be called Feynmanʼs Scientific Method,
and how by following that method we can become better scientists ourselves
and nurture the next generation of scientists.

Is gravity a fundamental force? I will discuss a few scenarios in which gravity emerges from the dynamics of some underlying field theory. In holography (or AdS/CFT correspondence), Einstein's equations for the bulk gravity dual are linked to entanglement in the boundary field theory. In another example, the graviton emerges as a composite spin two massless particle in a scalar field theory.

The ATLAS experiment is searching new territory for evidence of new particles produced in proton collisions at the highest energies.  Questioning assumptions is important in these searches. I will compare selected results from searches for supersymmetry with and without the assumption of R-Parity, a quantum number derived from the spin and type of particle.  I will also present some of the detector-related challenges associated with measuring charged particle momenta, including the planned upgrade of the detector to cope with up to 200 proton collisions every 25 nanoseconds.

I will review the current theoretical and phenomenological status of neutrino physics. In more detail, I will discuss our current understanding of neutrino properties, open questions, some new physics ideas behind nonzero neutrino masses, and the challenges of piecing together the neutrino mass puzzle. I will also comment on the new physics reach of the current and the next generation of neutrino oscillation experiments. 

Communication systems leverage the respective strengths of optics and electronics to convey high-bandwidth signals over great distances.  These systems were enabled by a revolution in low-optical-loss dielectric fiber, complex integrated circuits as well as devices that link together the optical and electrical worlds.  Today, another revolution is leveraging the advantages of optics and electronics in new ways.  At its center is the laser frequency comb which provides a coherent link between these two worlds. Significantly, because the link is also bidirectional, performance attributes previously unique to electronics and optics can be shared. The end result has been transformative for time keeping, frequency metrology, precision spectroscopy, microwave-generation, ranging and other technologies. Even more recently, low-optical-loss dielectrics, now in the form of high-Q optical resonators, are enabling the miniaturization of frequency combs. These new `microcombs’ can be integrated with electronics and other optical components to potentially create systems on-a-chip.  I will briefly overview the history and elements of frequency combs as well as the physics of the new microcombs. Application of the microcombs for spectroscopy and LIDAR will be discussed.  Finally, efforts underway to develop integrated optical clocks and integrated optical frequency synthesizers using the microcomb element are described.

It is customary for young physicists, when entering their professional career, to be astonished by the huge difference between physics as it is done and physics as it is taught. The purpose is to show that teaching of physics as it is done is indeed possible and should be encouraged, despite the undeniable existence of didactical, epistemological and institutional obstacles. 

There are currently several large telescope projects. One new telescope is the James Webb Space Telescope (JWST) which is planned to be launched into space on an Ariane 5 rocket from French Guiana in Spring 2019. It is expected that JWST will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System. The primary mirror will consist of 18 mirror segments made of beryllium coated with gold to give a total aperture diameter of 6.5 m. It is critical that the 18 mirror segments are properly phased so they perform as a single 6.5 m diameter mirror. JWST's backplane is the large structure that holds and supports the big hexagonal mirrors of the telescope. The backplane has an important job as it must carry not only the 6.5 m diameter primary mirror plus other telescope optics, but also the entire module of scientific instruments. The mechanical stability and thermal characteristics of the graphite composite backplane are extremely important for optimum performance of the telescope. JWST has many challenging optical testing requirements including a) Primary mirror figure testing, b) Back structure measurement, c) Segment phasing, d) Thermal and mechanical strain, and e) Vibrational dynamics.

Another telescope currently being constructed is the Giant Magellan Telescope (GMT), a large ground-based telescope consisting of seven 8.5 m diameter mirrors that will be built on a peak in the Andes Mountains near several existing telescope facilities at Las Campanas, Chile at an altitude of over 2,550 meters. The seven 8.4 m diameter mirror segments will be phased to give a telescope having the resolving power of a telescope 24.5 meters in diameter. GMT is expected to be operational for many decades, enabling breakthrough science ranging from studies of the first stars and galaxies in the universe to the exploration of extrasolar alien worlds. The GMT is poised to answer some of humanity’s biggest questions about the nature of exoplanets and whether we are alone in the universe, about the beginning of the universe to understand the formation and evolution of the galaxies, about the origin of the chemical elements, and how black holes grow. Like the JWST, the GMT has many challenging testing requirements.

During this talk we will describe the JWST and the GMT and the dynamic interferometry techniques that have been developed to measure high quality large telescope optics and the surface vibration and stability characteristics of the supporting structure required for high-quality performance large telescopes.

The recent gravitational wave observations of the collision of black holes and of neutron stars have allowed us to pierce into the extreme gravity regime, where gravity is simultaneously unfathomably large and wildly dynamical.  These waves encode a trove of information about physics that is prime for the taking, including potential revelations about the validity of Einstein's theory of General Relativity and about nuclear physics in the extreme gravity regime. In this talk, I will describe some of the inferences we can make on both theoretical and nuclear physics from current and future gravitational wave observations. 

The discovery of Dirac fermions in graphene has inspired a search for Dirac and Weyl semimetals in three dimensions thereby making it possible to realize exotic phases of matter first proposed in particle physics. Such materials are characterized by the presence of nontrivial quantum electronic states, where the electron’s spin is coupled with its momentum and Fermi surfaces are no longer closed contours in the momentum space, but instead consist of disconnected arcs. This opens up the possibility for developing new devices in which information is stored and processed using spin rather than charge. Such platforms may significantly enhance the speed and energy efficiency of information storage and processing. In this talk we will discuss the electronic properties of several of newly discovered tellurium based topological quantum materials. In WTe₂ we have observed a topological transition involving a change of the Fermi surface topology (known as a Lifshitz transition) driven by temperature. The strong temperature-dependence of the chemical potential that is at the heart of this phenomenon is also important for understanding the thermoelectric properties of such semimetals. In a close cousin, MoTe₂, by using high-resolution laser based Angle Resolved Photoemission Spectroscopy (ARPES) we identify Weyl points and Fermi surface arcs, showing a new type of topological Weyl semimetal with electron and hole pockets that touch at a Weyl point. I will also present evidence for a new topological state in PtSn₄, that manifests itself by presence of set of extended arcs rather than Dirac points, and so far is not yet understood theoretically. These results open up new directions for research aimed at enhancing topological responsiveness of new quantum materials.

Thoughts, memories, percepts, and actions all result from the interactions among large numbers of neurons.  Physicists have long hoped that these emergent behaviors could be described using ideas from statistical mechanics.  Recent experimental developments have made it possible to monitor, simultaneously, the electrical activity in hundreds or even thousands of cells.  I will describe surprisingly simple statistical physics models that provide a detailed, quantitative account of these data, and then turn to renormalization group ideas that allow us to search explicitly for some underlying simplicity.  There are signs that real networks are described by non-trivial fixed points, setting the stage for more ambitious theorizing.

http://www.princeton.edu/~wbialek/wbialek.html

In the four hundred years since Galileo, the physics community has constructed a remarkably successful mathematical description of the world around us.  From deep inside the atomic nucleus to the structure of the universe on the largest scales, from the flow air over the wing of an airplane to the flow of electrons in a computer chip, we can predict in detail what we see, and what will happen when we look in places we have never looked before.  What are the limits to this predictive power?  In particular, can we imagine a theoretical physicist’s approach to the complex and diverse phenomena of the living world?  Is there something fundamentally unpredictable about life, or are we missing some deep theoretical principles that could bring the living world under the predictive umbrella of physics?  Exploring this question gives us an opportunity to reflect on what we expect from our scientific theories, and on many beautiful phenomena.  I hope to leave you with a deeper appreciation for the precision of life’s basic mechanisms, and with optimism about the prospects for better theories. 

The recent discoveries of gravitational waves unveiled numerous opportunities in astrophysics, as well as in the study of the cosmos and the laws of physics.  In particular, the multi-messenger detection of binary neutron-star merger GW170817 through gravitational waves and across the electromagnetic spectrum already delivered several important results. I will outline what we learned from GW170817 so far (its remnant is still observable!), along with the opportunities and challenges of near-future multi-messenger observations that will broaden our horizon with gravitational waves in the next few years.  We can expect the proliferation of detected binary neutron star and binary black hole mergers, along with the large-scale efforts to rapidly identify the electromagnetic and neutrino counterparts of these events.  Frequent multi-messenger observations will enable the study of exceptional events, source populations, and sufficient statistics to probe new physics and cosmology.

The ability to probe and manipulate cold atoms in optical lattices at the atomic level using quantum gas microscopes enables quantitative studies of quantum many-body dynamics. While there are many well-developed theoretical tools to study many-body quantum systems in equilibrium, gaining insight into dynamics is challenging with available techniques. Approximate methods need to be benchmarked, creating an urgent need for measurements in experimental model  systems. In this talk, I will discuss two such measurements. First, I will present a study that probes the relaxation of density modulations in the doped Fermi-Hubbard model. This leads to a hydrodynamic description that allows us to determine the conductivity. We observe bad metallic behavior that we compare to predictions from finite-temperature Lanczos calculations and dynamical mean field theory. Second, I introduce a new platform to study the 2D quantum Ising model. Via optical coupling of atoms in an optical lattice to a low-lying Rydberg state, we observe quench dynamics in the resulting Ising model and prepare states with antiferromagnetic correlations.

The effects of band geometry on measurable properties of electronic systems have been one of the central subjects in the recent history of condensed matter physics. In this talk, I will describe how non-trivial topology and, more generally, geometry of gapless electronic phases manifest in their optical and transport characteristics.  The main focus of the talk will be on optical anomalous Hall effect and optical activity of Weyl metals, kinetic magnetoelectric effect in noncentrosymmetric conductors, as well as disorder physics in these materials. 

A gas of atoms cooled to sufficiently low temperature will form either a Bose-Einstein condensate (BEC) or a degenerate Fermi gas (DFG) depending on the quantum statistics of the constituent particles. But what happens when you combine a BEC and a DFG in an optical trap and add a healthy dose of interspecies interactions? Mean-field theory predicts three possible outcomes: a miscible mixture for weak interactions, complete demixing for strong repulsive interactions, or a spectacular collapse due to the loss of mechanical stability for strong attractive interactions. In this talk, I will discuss our efforts to answer this question experimentally in the specific case where the bosons are much heavier than the fermions. To this end, we have created the first quantum degenerate mixture of bosonic 133Cs and fermionic 6Li and used an interspecies Feshbach resonance to tune the interactions between the bosons and fermions. For attractive interspecies interactions, we find two surprising results. First,  we show that a degenerate Fermi gas of Li can be trapped by a Cs BEC, even in the absence of external potentials. Second, for strong attractive interactions where collapse is predicted, we observe no such instability. I will discuss the mechanisms at play to explain these results and comment on current and future studies delving deeper into these unexpected regimes.

Optics and photonics today enjoy unprecedented freedom. The ability to synthesize arbitrary light fields (through wavefront shaping) and the ability to design structures at the subwavelength scale (through nanofabrication) enable us to realize phenomena that could only be imagined in the past. In this talk, I will present several experiments and related theory that demonstrate exciting new phenomena which were previously inaccessible. A) Conventional textbook wisdom is that waves cannot be perfectly confined within the continuum spectrum of an open systems. Exceptions called “bound states in the continuum” were hypothesized by von Neumann and Wigner [1] but not realized. I will describe the first realization of such unusual states [2] and their manifestation as polarization vortices protected by topologically conserved “charges” [3]. B) Our ability to control radiation also enables the realization of non-Hermitian phenomena with no counterpart in closed systems. I will show how non-Hermiticity generates unique topologies in photonic band structures and lead to enhanced light–matter interactions [4,5]. C) Strong disorder in naturally occurring light-scattering media allows us to study mesoscopic physics in a new arena. I will describe the control of optical transport via wavefront shaping, and how the long-range correlations between multiply scattered photons enable us to simultaneously control orders of magnitudes more degrees of freedom than previously thought possible [6,7].

[1] C. W. Hsu*, B. Zhen* et al., Nature Reviews Materials 1, 16048 (2016).

[2] C. W. Hsu*, B. Zhen* et al., Nature 499, 188 (2013).

[3] B. Zhen*, C. W. Hsu* et al., Phys. Rev. Lett. 113, 257401 (2014).

[4] B. Zhen*, C. W. Hsu* et al., Nature 525, 354 (2015).

[5] H. Zhou et al., Science, eaap9859 (2018).

[6] C. W. Hsu et al., Phys. Rev. Lett. 115, 223901 (2015).

[7] C. W. Hsu et al., Nature Physics 13, 497 (2017).

Non-Hermitian systems exhibit rich physical phenomena that open the door to qualitatively new forms of control. In this talk, I will introduce our recent work on topological and nonreciprocal dynamics in a non-Hermitian optomechanical system. Specifically, we realized topological energy transfer between nearly degenerate modes by adiabatically encircling an exceptional point (a singularity of the complex spectrum). We also demonstrated that this energy transfer is non-reciprocal: a given topological operation can only transfer energy in one direction. We have extended the topological and nonreciprocal dynamics to highly non-degenerate modes by exploiting a generic form of nonlinearity, which should allow these effects to be exploited in a very wide range of physical systems. In addition, we realized nonreciprocal dynamics by optomechanical interference.

 

I will present a new formulation of quantum molecular dynamics for strongly correlated materials. Our novel scheme enables the study of the dynamical behavior of atoms and molecules with strong electron correlations. In particular, our scheme is based on the efficient Gutzwiller method that goes beyond the conventional mean-field treatment of the intra-atomic electron repulsion and captures crucial correlation effects such as band narrowing and electron localization. We use Gutzwiller quantum molecular dynamics to investigate the Mott metal-insulator transition in the liquid phase of a single-band metal and uncover intriguing structural and transport properties of the atoms. I will also discuss future plans for large-scale dynamical simulations of strongly correlated systems.

The heaviest elements in the periodic table are synthesized through the rapid neutron-capture process (r-process), but the astrophysical site producing these elements has been a long-standing conundrum. Ultra-faint dwarf galaxies contain a simple fossil record of early chemical enrichment that provide an ideal laboratory to investigate the origin of r-process elements. Previous measurements found very low levels of neutron-capture elements in ultra-faint dwarfs, preferring supernovae as the r-process site. I present high-resolution chemical abundances of nine stars in the recently discovered ultra-faint dwarf Reticulum II, which display extremely enhanced r-process abundances 2-3 orders of magnitude higher than the other ultra-faint dwarfs. Stars with such extreme r-process enhancements are only rarely found in the Milky Way halo. The r-process abundances imply that the neutron-capture material in Reticulum II was synthesized in a single prolific event that is incompatible with r-process yields from ordinary core-collapse supernovae but consistent with a neutron star merger. Together with the recent gravitational wave observations of a neutron star merger and its electromagnetic afterglow, it is now clear that neutron star mergers dominate cosmic production of r-process elements.

Wolfgang Pauli called solid-state physics "the physics of dirt effects", and this name might appear well-deserved at first sight since transport properties are more often than not set by extrinsic properties, like impurities. In this talk, I will present solid-state systems in which electrons behave hydrodynamically, and for which transport properties are instead set by intrinsic properties, like the viscosity. This new regime of transport opens the way for a “viscous electronics”, and provides a new angle to study how quantum mechanics can constrain and/or enrich hydrodynamics.

Quantum computers can solve certain problems more efficiently than any classical computer. Trapped ions are a promising candidate for realizing such a system. We present a modular quantum computing architecture comprised of a chain of 171Yb+ ions with individual Raman beam addressing and individual readout [1]. We use the transverse modes of motion in the chain to produce entangling gates between any qubit pair. This creates a fully connected system which can be configured to run any sequence of single- and two-qubit gates, making it in effect an arbitrarily programmable quantum computer that does not suffer any swap-gate overhead [2].
Recent results from different quantum algorithms on five and seven ions will be presented [3,4], including a quantum error detection protocol that fault-tolerantly encodes a logical qubit [5]. I will also discuss current work and ideas to scale up this architecture.

[1] S. Debnath et al., Nature 563:63 (2016).
[2] NML et al., PNAS 114 13:3305 (2017).
[3] C. Figgatt et al., Nat. Communs. 8, 1918 (2017).
[4] NML et al., arXiv:1712.08581 (2017)
[5] NML et al., Sci. Adv. 3, 10 (2017).

 

Quantum optics has had a profound impact on precision measurements, and recently enabled probing various physical quantities, such as magnetic fields and temperature, with nanoscale spatial resolution. Such advancements in ‘quantum sensing’ have brought the elusive dream of performing nuclear magnetic resonance spectroscopy (NMR) on individual biomolecules closer to reality. In my talk, I will discuss the development and application of novel quantum metrological technologies to study biological systems at a single-molecule level. I will start with a general introduction to quantum sensing, with a focus on the measurement of magnetic fields at a nanoscale. I will then show how we utilize such sensing techniques to control the temperature profile in living systems with subcellular resolution. Finally, I will provide an outlook on how quantum sensing and single-molecule biophysics can be utilized to perform NMR spectroscopy with unprecedented sensitivity, possibly down to the level of individual biomolecules.

 

Topological superconductors exhibit exotic Majorana modes at the boundaries and vortices, and can provide important applications in quantum computing. In addition to usual path of “engineering” topological superconductivity with heterostructure of conventional superconductors, we show that intrinsic topological superconductivity can also be naturally realized through electron-electron interactions. Specifically, we analyze the topological superconducting state that emerges near the onset of an inversion-breaking electronic order. Other than topological superconductivity, we show that the system has an enhanced U(1)xU(1) symmetry as well as a rich phase diagram. We address the relevance of our results with recent experiments in Cd2Ce2O7 and half-Heusler superconductors. We argue that important progress can be made at the intersection of topological superconductivity and unconventional superconductivity.

Amorphous solids are omnipresent in everyday life, from window glasses to plastics to piles of sand. Yet our understanding of their properties lags far behind that of their crystalline counterparts. Recent advances are rapidly changing the way in which we understand these materials. This talk overviews two such advances: (i) the algorithmic developments that link dramatic slowdown of glass-forming liquids to growing amorphous order, and (ii) the discovery of the critical replica-symmetry-breaking transition within solid glasses. Taken together, these results reinforce the overriding role of rugged free-energy landscapes in controlling glassiness.

The past decade's apparent success in predicting and experimentally discovering distinct classes of topological insulators (TIs) and semimetals masks a fundamental shortcoming: out of 200,000 stoichiometric compounds extant in material databases, only several hundred of them are topologically nontrivial. Are TIs that esoteric, or does this reflect a fundamental problem with the current piecemeal approach to finding them? To address this, we propose a new and complete electronic band theory that highlights the link between topology and local chemical bonding, and combines this with the conventional band theory of electrons. We classify the possible band structures for all 230 crystal symmetry groups that arise from local atomic orbitals, and show which are topologically nontrivial. We show how our topological band theory sheds new light on known TIs, and demonstrate the power of our method to predict new TIs.

States of a multiparticle quantum system are useful for quantum information processing when they are entangled, i.e., not product states relative to the tensor product decomposition of the Hilbert space corresponding to the particles.  Arbitrary entanglements between parts of a quantum system are not possible, however; they must satisfy certain “monogamy” constraints which limit how much multiple different subsystems can be entangled with one another.  The standard monogamy constraints can be generalized in several ways:  in this talk we’ll tighten some, generalize others to higher dimensional tensor factors, and derive inequalities satisfied by symmetric sets of entanglement measures.  Along the way we’ll contrast the quantum results with corresponding statements about classical random variables. 

https://math.ucsd.edu/people/profiles/david-meyer/

In classical mechanics, chaos refers to the phenomenon that an arbitrarily small perturbation leads to a dramatic change at a later time. The analogous phenomenon in quantum mechanics---quantum chaos is generic in many-body systems. Although chaos makes it difficult to solve the many-body problem exactly, it actually provides new knowledge about dynamics of the system, such as thermalization. In understanding quantum chaos and thermalization, the concept of quantum entanglement plays an essential role. In this talk, I will discuss the connection between several related phenomena, including the dynamics of quantum entanglement, thermalization of isolated systems, and measure of quantum chaos. As a concrete model to study quantum chaos, I will discuss the Sachdev-Ye-Kitaev (SYK) model and its generalizations. This model provides an example of strongly correlated systems in which new kinds of "order" emerges from chaos. Entanglement dynamics in this model suggests an interesting interplay between thermalization and many-body localization.

References: arXiv:1511.04021

arXiv:1609.07832 

arXiv:1708.00871

Recent theoretical advances in the mean-field theory of glasses predict the existence, deep in the glass phase, of a novel phase transition, a so-called Gardner transition. This transition signals the emergence of a complex free energy landscape composed of a marginally stable hierarchy of sub-basins. It is also thought to be the onset of the anomalous thermal and transport properties of amorphous systems, and to ultimately lead to the unusual critical behavior at jamming. In this talk, I will present an overview of our recent theoretical and numerical advances in capturing and characterizing this novel materials feature.

According to early ideas of Mott and Anderson, the interaction-­driven metal-­insulator transition “the Mott transition“ remains a sharp T=0 phase transition even in absence of any spin or charge ordering.  Should this phase transition be regarded as a quantum critical point?  To address this question, here we examine the phase diagram and transport properties of the maximally frustrated half-­filled Hubbard model, in the framework of dynamical mean-­field theory (DMFT).  We identify a quantum Widom line (QWL) which defines the center of the corresponding quantum critical region associated with Mott metale insulator transition for this model.  The evolution of resistivity with temperature is then evaluated along trajectories following (parallel to) the QWL, displaying remarkable scaling behavior characteristic of quantum criticality.  Precisely this kind of behavior was found in very recent experiments on organic Mott systems [1,2].  In the case of the doping-driven Mott transition, we show that the mysterious Bad Metal behavior (T-linear resistivity around the Mott-Ioffee- Regel limit) coincides with the Quantum Critical region of the Mott transition.

[1] Quantum criticality of Mott transition in organic materials, Tetsuya Furukawa, Kazuya Miyagawa, Hiromi Taniguchi, Reizo Kato & Kazushi Kanoda, Nature Physics, 9 Feb.  2015; doi:10.1038/nphys3235.

[2] See also:

http://condensedconcepts.blogspot.com/2015/03/quantum-criticality-near-mott.html

In nearly every science, math, and engineering field there is a significant falloff in participation by underrepresented minority (URM) students who fail to make the transition between undergraduate and graduate studies.  The American Physical Society (APS) has realized that a professional society can erase this gap by acting as a national recruiter of URM physics students and connecting these individuals with graduate programs that are eager to a) attract motivated students to their program, b) increase domestic student participation, and c) improve the diversity of their program.  Now in its fifth year the APS has placed enough students into graduate programs nationwide to eliminate this achievement gap.  The program has low costs, is popular among graduate programs, and has inspired other departments to adopt practices that improve graduate admissions and student retention. This presentation will review project activities, present data that demonstrate effectiveness, and discuss future actions.

This material is based upon work supported in part by the National Science Foundation under Grant No. (NSF-1143070).

Homodyne measurement is a corner-stone of quantum optics. It measures the fundamental variables of quantum electrodynamics - the quadratures of light, which represent the cosine-wave and sine-wave components of an optical field. The quadratures constitute the quantum optical analog of position and momentum in mechanics and obey quantum uncertainty, indicating the inherent inability to measure both simultaneously. The homodyne process, which extracts a chosen quadrature amplitude by correlating the optical field against an external quadrature reference (local-oscillator, LO), forms the backbone of coherent detection in physics and engineering, and plays a central role in quantum information processing. Homodyne can reveal non-classical phenomena, such as squeezing of the quadrature uncertainty; It is used in tomography to fully characterize quantum states of light; Homodyne detection can generate non-classical states, provide local measurements for teleportation and serve as a major detector for quantum key distribution (QKD) and quantum computing. Yet, standard homodyne suffers from a severe bandwidth limitation. While the bandwidth of optical states can easily span many THz, standard homodyne detection is inherently limited to the electrically accessible, MHz to GHz range, leaving a dramatic gap between the relevant optical phenomena and the measurement capability. This gap impedes effective utilization of the huge bandwidth resource of optical states and the potential enhancement of the information throughput \emph{by several orders of magnitude} with parallel processing in quantum computation, QKD and other applications of quantum squeezed light. Here we demonstrate a fully parallel optical homodyne measurement across an arbitrary optical bandwidth, effectively lifting the bandwidth limitation completely. Using optical parametric amplification, which amplifies one quadrature while attenuating the other, we measure two-mode quadrature squeezing of 1.7dB below the vacuum level simultaneously across a bandwidth of 55THz using a single LO - the pump. This broadband parametric homodyne measurement opens a wide window for parallel processing of quantum information.

Yaakobv Shaked, Yoad Michael, Rafi Vered, Leon Bello, Michael Rosenbluh and Avi Pe'er, Physics Dept. and BINA center for  Nanotechnology, Bar Ilan University, Ramat Gan 5290002, Israel

The history of our exploration of subatomic matter has witnessed a major breakthrough with every new probe being introduced. In the 1950’s Hofstadter and collaborators using elastic electron scattering measured for the first time the electromagnetic form factors of nucleons and nuclei and provided the first information on the nuclear spatial charge and magnetization distributions. In the late 1960’s and early 70’s, Friedman, Kendall and Taylor using Deep Inelastic Scattering of electrons off the nucleon, discovered its underlying quark structure displayed in their longitudinal momentum distributions. 

I will discuss probes at the next frontier that will allow us to access dynamically correlated distributions in both momentum and coordinate space -- the Wigner distributions -- at the femtoscale. Deeply Virtual Compton Scattering, namely a high energy lepton scattering off a nucleon target producing a high energy real photon and a small angle recoil proton, is one of such probes. I will explain how a detailed mapping of the quarks and gluons in the nucleon and nucleus in phase space, or a phase-space tomography, besides providing for the first time images of quarks and gluons spatial distributions, is essential for understanding the so far elusive nucleon mass and spin decompositions in terms of its quark and gluon components. 

Quantum internet of the future will require device functionalities that implicitly respect the fundamental facts such as quantum information cannot be copied, and cannot be measured precisely. A quantum repeater, for example,—analog of an optical amplifier that enabled global reach of the ubiquitous Internet connectivity we enjoy today—is yet to be demonstrated, although recent years have seen tremendous progress. Many other device functionalities—switches, routers, format converters, etc.—would also be needed that do not unnecessarily disturb or corrupt the quantum information as it flows from one node of the internet to another. In recent years, my group has engineered an all-optical quantum switch that fulfills many of the requirements for distributing quantum information in a networked environment. In this talk, I will present our motivation, design, construction, characterization, and utilization of such a switch in near-term networked quantum applications.

The measurement of the violation of parity symmetry in electron scattering has proven to be a powerful technique for exploring nuclear matter and searching for new fundamental forces. In the Standard Model of particle physics, parity violation can only occur through the weak interaction. Precision measurements of this symmetry breaking can test the completeness of this description of the weak force at low energies. I will describe the result of one such measurement - the recently completed Qweak experiment - along with the experimental challenges and triumphs.  Future measurements in the field of parity-violating electron scattering will also be reviewed, including other Standard Model tests and experiments using the weak force to determine the size of a heavy atomic nucleus.

The word "atom" (a-tomos) originates from ancient Greek philosophers, who argued that objects can be eventually divided into discrete, small particles, beyond which matter is no longer cuttable.  Our search for the answer to "What the matter is made of" has gone a long way, from the first experimental evidence of atoms in the 1800's, to Rutherford's alpha scattering on gold foils, to modern day's linear accelerators looking into the atomic nucleus. We now understand that matter is made of quarks and leptons, currently named elementary particles (objects of no size) that form the foundation of the Standard Model of Particle Physics. However, if we look back at this journey, one may wish to oppose the view of the ancient Greeks and argue that quarks and leptons cannot be the end of the story, that our quest for peeling the atomic onion may be a timeless journey.

I will discuss the frontier research in electron scattering at the GeV energy level. I will focus on parity violation in electron scattering off the proton and the neutron and the extraction of neutral-weak effective couplings between electrons and quarks, and show how such high precision measurements are now helping us venturing further into the study of subatomic structure. 

The Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves for the first time in 2015. Since then there have been a couple more detections of binary black hole mergers. I will discuss the instruments that made these discoveries, the science so far, and plans for future improvements and upgrades to LIGO. 

In 2016, scientists announced the first ever detection of gravitational waves from colliding black holes, launching a new era of gravitational wave astrophysics. Gravitational waves were predicted by Einstein a hundred years earlier. I will describe the science, technology, and human story behind these discoveries that provide a window into some of the most violent and warped events in the Universe.

 

When you shine a laser on an atom, the electric field of the light induces a dipole moment, resulting in an energy shift. The dipole can be either parallel or anti-parallel to the field, depending on the frequency of the light. This corresponds to negative or positive energies. At certain frequencies, however, the induced dipole is zero. The corresponding light wavelength is called a tune-out wavelength. The location of the various tune-out wavelengths depend on the electronic wave function in the atom, particularly the dipole matrix elements . So by measuring the tune-out wavelength, the dipole matrix elements can be determined more accurately than by conventional techniques. This is useful because the dipole matrix elements are also used to relate precision atomic experiments like parity violation to fundamental particle properties like the weak mixing angle. We have developed a new technique for measuring  tune-out wavelengths, which should improve our knowledge of many matrix elements by an order of magnitude or more. We hope that this will support new generations of precision atomic measurements.

Long carrier lifetime is what makes hybrid organic-inorganic perovskites high performance photovoltaic materials. Several microscopic mechanisms behind the unusually long carrier lifetime have been proposed, such as formation of large polarons, Rashba effect, ferroelectric domains, and photon recycling. Here, we show that the screening of band-edge charge carriers by rotation of organic cation molecules can be a major contribution to the prolonged carrier lifetime. Our results reveal that the band-edge carrier lifetime increases when the system enters from a phase with lower rotational entropy to another phase with higher entropy. These results imply that the recombination of the photo-excited electrons and holes is suppressed by the screening, leading to the formation of polarons and thereby extending the lifetime. Thus, searching for organic-inorganic perovskites with high rotational entropy over a wide range of temperature may be a key to achieve superior solar cell performance.

For over 50 years, people have been discussing the promise of high-energy neutrino astronomy.  For most of that time, wholesale theoretical conjecture was unmatched by even a trifling return of measured experimental facts.  Then in 2013, the IceCube neutrino observatory discovered astrophysical neutrinos with energies up to fifteen orders of magnitude above those of visible light.  What does this mean for understanding astrophysical sources, the properties of neutrinos, and the contents of the Universe?

Short x-ray pulses from free electron lasers (FELs) open a new regime for all scientific research. The first x-ray FEL, the Linac Coherent Light Source (LCLS) at the SLAC National Laboratory on the Stanford campus, provides intense short pulses that allow the investigation of ultrafast non-linear and multi-photon processes, including time-resolved investigations in molecules. We will report on the femtosecond response of molecules to the ultra-intense, ultrafast x-ray radiation from FELs as well as on time-resolved investigation using x-ray pump-x-ray probe techniques.

Quantum-critical strongly correlated systems feature universal collision-dominated collective transport. Viscous electronics is an emerging field dealing with systems in which strongly interacting electrons flow like a fluid. We identified vorticity as a macroscopic signature of electron viscosity and linked it with a striking macroscopic DC transport behavior: viscous friction can drive electric current against an applied field, resulting in a negative resistance, recently measured experimentally in graphene. I shall also describe current vortices, expulsion of electric field, conductance exceeding the fundamental quantum-ballistic limit and other wonders of viscous electronics. Strongly interacting electron-hole plasma in high-mobility graphene affords a unique link between quantum-critical electron transport and the wealth of fluid mechanics phenomena.

http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3667.html

https://arxiv.org/abs/1607.00986  

http://arxiv.org/abs/1607.07269

Quantum thermodynamics has emerged as an interdisciplinary research field in quantum science and technology with widespread applications. Yet, the identification of scenarios characterized by quantum supremacy -a performance without match in the classical world- remains challenging. In this talk I shall review recent advances in the engineering and optimization of quantum thermal machines. I will show that nonadiabatic many-particle effects can give rise to quantum supremacy in finite-time thermodynamics [1]. Tailoring such nonadiabatic effects by making use of shortcuts to adiabaticity, quantum heat engines can be operated at maximum efficiency and arbitrarily high output power [2]. A thermodynamic cost of these shortcuts will be elucidated by analyzing the full work distribution function and introducing a novel kind of work-energy uncertainty relation [3]. I shall close by discussing the identification of scenarios with a quantum-enhanced performance in thermal machines run over many cycles [4]. 

Bibliography: 
[1] J. Jaramillo, M. Beau, A. del Campo, New J. Phys. 18, 075019 (2016). 
[2] M. Beau, J. Jaramillo, A. del Campo, Entropy 18, 168 (2016). 
[3] K. Funo, J.-N. Zhang, C. Chatou, K. Kim, M. Ueda and A. del Campo, Phys. Rev. Lett, 118, 100602 (2017).
[4] G. Watanabe, B. P. Venkatesh, P. Talkner and A. del Campo, Phys. Rev. Lett. 118, 050601 (2017).

The high energy density and low cost of lithium-ion batteries have created a revolution in personal electronics through laptops, tablets, smart phones and wearables, permanently changing the way we interact with people and information.  We are at the threshold of similar transformations in transportation to electric cars and in the electricity grid to renewable generation, smart grids and distributed energy resources.  Many aspects of these transformations require new levels of energy storage performance and cost that are beyond the reach of Li-ion batteries.  Next generation beyond Li-ion batteries and their potential to meet these performance and cost thresholds will be analyzed.

George Crabtree, Elizabeth Kocs and Lynn Trahey, The energy-storage frontier: Lithium-ion batteries and beyond, MRS Bulletin 40, 1067 (2015)

Bio: George Crabtree is Director of the Joint Center for Energy Storage (JCESR) at Argonne National Laboratory and Professor of Physics, Electrical, and Mechanical Engineering at University of Illinois-Chicago (UIC).  He has wide experience in next-generation battery technology and integrating energy science, technology, policy and societal decision-making. He has led workshops for the Department of Energy on energy science and technology, is a member of the National Academy of Sciences and has testified before the U.S. Congress. 

The High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory was completed in March 2015 and is now giving us a new view of the sky. HAWC is a continuously operating, wide field-of-view observatory sensitive to 100 GeV – 100 TeV gamma rays and cosmic rays. It is 15 times more sensitive than previous generation extensive air shower gamma-ray instruments. It serves as a “finder” telescope and monitors the same sky as gamma-ray satellites (Fermi), gravity-wave (LIGO) detectors and neutrino observatories (IceCube) allowing for multi-wavelength and multi-messenger observations.  HAWC hopes to answer questions such as "what is dark matter?” and “where do cosmic rays come from?” by observing some of the most violent processes in our Universe. I will present highlights from HAWC’s first year of operation.

Understanding how cells control and coordinate the various ongoing cellular processes, such as DNA replication, growth and division is an outstanding fundamental problem in biology. Remarkably, bacterial cells may divide faster than their chromosomes replicate, implying that cells maintain multiple rounds of chromosome replication, and that tight control over DNA replication must be in place. I will show how ideas from statistical mechanics and mathematical modeling can serve as alternative "microscopes" into this problem. Our results suggest that both cell size and chromosome replication may be simultaneously regulated by following a simple control mechanism, in which, effectively, a constant volume is added between two DNA replication initiation events. This model elucidates the experimentally observed correlations between various events in the cell cycle, and explains the exponential dependence of cell size on the growth rate, as well as recent experiments in which cell morphology is perturbed.

http://amir.seas.harvard.edu/

The IceCube project at the South Pole has melted eighty-six holes over 1.5 miles deep in the Antarctic icecap for use as astronomical observatories. The project recently discovered a flux of neutrinos reaching us from the cosmos, with energies more than a million times those of the neutrinos produced at accelerator laboratories. These neutrinos are astronomical messengers from some of the most violent processes in the universe--giant black holes gobbling up stars in the heart of quasars and gamma-ray bursts, the biggest explosions since the Big Bang.

In a special public lecture, brought to you by the departments of physics, astronomy, and NRAO Francis Halzen, Gregory Breit Professor and Hilldale Professor of Physics at UW-Madison and the principal investigator of IceCube, will tell the story of the IceCube telescope and discuss highlights from recent scientific results.

Physicists have used light and its polarization to elucidate the internal state of atoms since the 19th century.  Early in the 20th century, the momentum of light was used to change the center-of-mass motion of atoms.  The latter part of the 20th century brought optical pumping, coherent laser excitation, and laser cooling and trapping as tools to manipulate both the internal and external states of atoms.  Atom optics techniques like diffraction of atoms from light provided the elements needed for atom-wave interferometers.  Bose-Einstein condensation created atomic samples having laser-like deBroglie-wave coherence.   Now, in the 21st century, the circulation of superfluid atoms in ring-shaped structures enables “atomtronic” circuitry—an atomic analog of superconduction electric circuits.  We observe persistent flow of atoms in toroidal traps, and can introduce a weak-link (a kind of Josephson junction) that allows control of the quantized circulation of atoms. 

Black holes and neutron stars are extraordinary astrophysical laboratories.

They allow us to test the laws of gravity and nuclear physics in extreme environments which cannot be reproduced on Earth. In this talk, I will discuss efforts to model these compact objects in two classes of astrophysical systems: mergers of black hole-neutron star and neutron star-neutron star binaries, and accretion disks around supermassive black holes. The first are powerful sources of gravitational waves, and emit bright electromagnetic transients. In the advanced gravitational wave detector era, they will provide us with new information about general relativity, the properties of matter above nuclear density, and the population of black holes and neutron stars. The second will soon be imaged by the Event Horizon Telescope with enough accuracy to resolve the horizon of two black holes, and to study the behavior of the nearly collisionless plasma accreting onto them. I will in particular focus on the role of numerical simulations using general relativistic codes, which will play a crucial role in our interpretation of these upcoming observations.

Recent work on topological materials has revealed a wide variety of intriguing phenomena that may arise when particles move in "non-trivial" bands.  At the same time, modern advances in experimental capabilities for controlling electronic, atomic, and optical systems open new possibilities for dynamically controlling the behaviors of a range of quantum systems. In this talk I will review the basic ideas behind topological band theory, and then explain how periodic driving can be used to gain dynamical control over the topological properties of quantum matter.  In the driven case, intriguing new types of robust non-equilibrium topological phenomena emerge. To illustrate, I will show how the combination of driving, topology, and interactions can bring about a new regime of universal quantized transport, and discuss potential near-term experimental realizations.

**THE RECEPTION WILL BE HELD AT 3:00PM IN ROOM 313**

In the next few years, low-frequency radio telescopes will use the 21cm line of neutral hydrogen to make unprecedentedly large maps of our observable Universe. These will provide exquisite constraints on the properties of the first stars and galaxies. Along these lines, I will review recent results from the Precision Array to Probe the Epoch of Reionization (PAPER) experiment, which have begun to shed light on heating processes in the early universe. I will also discuss how comparing theory and observations will become difficult as one enters the regime of “big data” and theoretical models become increasingly complicated. I will describe how machine learning techniques make such comparisons computationally feasible. Finally, I will discuss the recently commenced Hydrogen Epoch of Reionization Array (HERA) experiment, including its forecasted ability to constrain fundamental parameters such as the neutrino mass. Looking to the future, I will highlight additional opportunities to constrain cosmology and particle physics using the 21cm line.

I will discuss a promising design proposal for a scalable topological quantum computer. The qubits are envisioned to be encoded in aggregates of four or more Majorana zero modes, realized at the ends of topological superconducting wire segments that are assembled into superconducting islands with significant charging energy. Quantum information can be manipulated according to a measurement-only protocol, which is facilitated by tunable couplings between Majorana zero modes and nearby semiconductor quantum dots. The key virtue of the proposed architecture is its modular and scalable design and a natural suppression of quasiparticle poisoning by charge protection.

In the second part of the talk I will comment on the importance of elevating these designs to full quantum universality by so called magic state injection. The latter relies on a high fidelity source of specific quantum states and I will point out some of ideas and challenges for providing them.

**THE RECEPTION WILL BE HELD AT 3:00PM IN ROOM 313**

On September 14, 2015, the two LIGO detectors simultaneously observed a transient gravitational-wave signal, which was named GW150914. The signal fit very precisely the general-relativistic prediction for the inspiral, merger, and ringdown of a pair of stellar-mass black holes, with component masses greater than was thought possible in standard evolution scenarios. This was the first direct detection of gravitational waves and the first observation of a binary black-hole merger. I describe the mechanics and behind-the-scenes of the detection, and its implications for astrophysics and fundamental physics. Two additional black-hole binaries were detected in LIGO's first observing run, and more are expected from current data taking. At the low-frequency side of the gravitational-wave spectrum, signals from massive black-hole binaries are targeted by the space-based observatory LISA, now on track for launch in the early 2030s, and by pulsar-timing arrays, with a positive detection expected in ten years. I discuss the science case, prospects, and requirements of these programs.

**THE RECEPTION WILL BE HELD AT 3:00PM IN ROOM 313**

Topological phases of matter is an active research area of condensed matter physics. Among various topics, the bosonic symmetry protected topological (BSPT) states have attracted enormous theoretical interest in the last few years. BSPT states are bosonic analogs of topological insulators. The Haldane phase of spin-1 chains is one famous example. I will talk about our recent proposal to realize two-dimensional BSPT states in the twisted bilayer graphene with strong magnetic field, as well as numerical simulations of the lattice model in various parameter regimes. The proposed BSPT state is a quantum spin Hall insulator with bosonic boundary modes only. The bosonic modes are spin and charge collective excitations of electrons. The quantum phase transition between the topological and the trivial phases happens by closing the gap of bosonic modes in the bulk, without closing the single particle gap of electrons, which is fundamentally different from all the well-known topological transitions in free fermion topological insulators. On the theory side, the phase transition is related to topics of deconfined criticality and duality of (2+1)D conformal field theories. The theoretical, numerical and experimental studies will deepen our understanding of quantum phase transitions.

**THE RECEPTION WILL BE HELD AT 3:00PM IN ROOM 313**

Black holes and neutron stars are extremely compact astrophysical objects that are produced after the death of very massive stars. Due to their large compactness and population, such compact objects offer us excellent testbeds for probing fundamental physics. In this talk, I will focus on probing extreme (strong and dynamical-field) gravity that was previously inaccessible. Regarding black hole based tests of gravity, I will explain how stringently one can probe various fundamental pillars in General Relativity with the recently-discovered gravitational wave events. Regarding neutron star based tests of gravity, I will use approximate universal relations ("I-Love-Q relations") among certain neutron star observables that are almost insensitive to the unknown stellar internal structure, and describe how one can probe extreme gravity by combining future gravitational wave and binary pulsar observations. I will conclude with a summary of important future directions.

In my talk, I review recent and not so recent works aiming to understand whether a nominally repulsive Coulomb interaction can by itself give rise to a superconductivity.  I discuss a generic scenario of the pairing by electron-electron interaction, put forward by Kohn and Luttinger back in 1965, and  modern studies of  the electronic mechanisms of superconductivity in the lattice systems which model cuprates,  Fe-pnictides, and  doped graphene.  I show that the pairing in all three classes of materials can be viewed as a lattice version of Kohn-Luttinger physics, despite that the pairing symmetries are different.  I discuss under what conditions the pairing occurs and rationalize the need to do  renormalization-group studies.  I also discuss the interplay between superconductivity and density-wave instabilities.

Metal joining is a controlled process used to fuse metals. There are several techniques of metal joining of which friction stir welding is one of the more basic forms. Friction stir welding is an innovative weld process that continues to grow in use, in the commercial, defense, and space sectors. It produces high quality and high strength welds in aluminum alloys. The process consists of a rotating weld pin tool that plasticizes material through friction. The plasticized material is welded by applying a high weld forge force through the weld pin tool against the material during pin tool rotation.  Self-reacting friction stir welding (SR-FSW) is one variation of the FSW process developed at the National Aeronautics and Space Administration (NASA) for use in the fabrication of propellant tanks and other areas used on the Space Launch System (SLS)

NASA's SLS is an advanced, heavy-lift launch vehicle which will provide an entirely new capability for science and human exploration beyond Earth's orbit. The SLS will give the nation a safe, affordable and sustainable means of reaching beyond our current limits and open new doors of discovery from the unique vantage point of space.

In this talk, I will focus on cosmologies that replace the big bang with a big bounce. I will explain how, in these scenarios, the large-scale structure of the universe is determined during a contracting phase before the bounce and will describe the recent development of the first well-behaved classical (non-singular) cosmological bounce solutions.

The nature of dark matter is one of the most longstanding and puzzling questions in physics. With cosmological measurements we have been able to measure its abundance with great precision. Yet, what dark matter is composed of remains a mystery.

In 2016 the first ever observation of gravitational waves from the coalescence event of two black holes was achieved by the LIGO interferometers.

Together with my collaborators we recently advocated that the interactions of 30 solar masses primordial black holes composing the dark matter could explain this event.

This opens up a new window in indirect searches for dark matter.

In my talk, I will discuss the various probes to distinguish between these mergers of primordial black holes, from the more traditional astrophysical black hole binaries.

One is through their mass spectrum, another is through cross-correlation of gravitational events with future overlapping galaxy catalogs. A third, is through their contribution to the stochastic gravitational wave background. Finally a fourth probe uses the fact that primordial black black holes form binaries with highly eccentric orbits. Those will then merge on timescales that in some cases are years, days or even minutes, retaining some eccentricity in the last seconds before the merger, which can be detected by LIGO and future ground based interferometers.

Graphene in its pristine form has transformed our understanding of 2D electron systems leading to fundamental discoveries and to the promise of important applications. I will discuss new and surprising phenomena that emerge when the perfect honeycomb lattice of graphene is disrupted. In particular I will focus on the effects of single atom vacancies on graphene's electronic and magnetic properties as revealed by scanning tunneling microscopy and spectroscopy. These include charging the vacancy site into the supercritical regime where we observe the formation of an artificial 2D atom 1,  and electrostatically controlled Kondo screening of the vacancy magnetic moment.

1 J.Mao, Y.Jiang, D. Moldovan,  G. Li,  K. Watanabe, T. Taniguchi,   M. R. Masir, F.M. Peeters, E.Y. Andrei, Tunable Artificial Atom at a Supercritically Charged Vacancy in Graphene, Nature Physics 2016, doi:10.1038/nphys3665

DES is an ongoing imaging sky survey, the largest such survey to date. Its main science goal is to shed light onto dark energy by making precision measurements of the expansion history and growth of structure in the universe. In this talk I present an overview of our latest results and introduce a new DES initiative: searches for optical counterparts to gravitational wave events.

A public lecture by Adam Reiss, recipient of the 2011 Nobel Prize for the detection of the accelerating expansion of the universe using distant supernovas.  The lecture will be presented at 7 pm on Wednesday, November 9, at the Paramount Theater on Charlottesville's Downtown Mall.

The  Physics  and  Astronomy  Departments  at  the  University  of Virginia in partnership the National Radio Astronomy Observatory invite the community to a special FREE public  lecture  by  Nobel  Laureate  Adam  Riess  at  The  Paramount  Theater  on  Wednesday,  November  9  at 7:00PM.    Prof.  Riess  will  speak  on  the  fascinating  topic  of  the  accelerating  universe.  Due  to  his  critical contributions, Prof. Riess shared the 2011 Nobel Prize "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae."  The term "supernovae" refers to stars exploding at the end of their lives. The team Prof. Riess worked with used a particular kind of supernova, called type Ia supernova,  to  understand  the  properties  of  distant  galaxies.    His  research  team  found  that  light  from distant  supernovae  was  weaker  than  expected  ‐  this  was  a  sign  that  the  expansion  of  the  Universe  was accelerating. Prof. Riess will discuss the excitement of this discovery, its implications, and current ongoing work to help answer remaining questions. 

https://conference.phys.virginia.edu/indico/event/1/page/14-the-accelerating-universe-public-lecture-by-nobel-laureate-adam-riess

Some 40 years ago Hawking found a remarkable contradiction: if we accept the standard behavior of gravity in regions of low curvature, then the evolution of black holes will violate quantum mechanics. Resolving this paradox would require a basic change in our understanding of spacetime and/or quantum theory. This paradox has found an interesting resolution through string theory. While quantum gravity is normally expected to be important only at distances of order planck length, the situation changes when a large number N of particles are involved, as for instance in the situation where we make a large black hole. Then the length scale of quantum gravity effects grows with N, altering the black hole structure to a "fuzzball"; this effect resolves the paradox.

An objective overview of the nuclear arms race will be presented with an emphasis  on the present situation. A brief sketch of how nuclear weapons work and some ironic lessons from history will be presented. Scientists' discussions about preventing proliferation and use started in the secrecy of the Manhattan Project and continued in public during the rapid cold war buildup to the present (e.g., Bulletin of the Atomic Scientists). The central role of the nuclear non-proliferation treaty, the Iran agreement, possible pathways to nuclear conflict, and a personal view of the outlook to prevent future nuclear weapons use, including the vital role of education, will be presented.

 Aron Bernstein is Professor of Physics, Emeritus, MIT. His physics research has focused on experimental tests of the symmetries of the standard model (chiral anomaly and symmetry). He has followed the nuclear arms race carefully since the Cuban Missile Crisis, has taught courses on this subject, and has done research on arms control issues such as the dangers posed by the Russian and US short ballistic missile launch and warning times. He is a National Board Member of the Council for a Livable World, started by physicist Leo Szilard, which works with Congress on nuclear arms control issues.

We have bombarded chiral halocamphor molecules in the gas phase with low-energy (< 1 eV), longitudinally-spin-polarized electrons, and investigated dissociative electron attachment (DEA) reactions:

e- + HA → H- + A,

where H is a halogen atom (Br or I) and A is the residual camphor fragment.  We observe that for a given target handedness, the total DEA cross section depends on the helicity of the incident electron.  In the case of iodocamphor at the lowest incident electron energies, this effect can be as large as two parts in 1000.  The observation of chiral sensitivity in a break-up reaction is important because, among other things, it validates the premise of the Vester-Ulbricht hypothesis regarding the origins of biological homochirality.  The sordid history of previous attempts to demonstrate such effects will be briefly reviewed.

On February 11, LIGO scientists announced the direct detection of gravitational waves, confirming a century-old prediction of Einstein's general theory of relativity.  This milestone was finally made possible with the incredibly sensitive Advanced LIGO detectors, combined with a certain measure of luck. This first event is already enough to investigate the properties of the source, test the theory of gravity, and project what more we can learn from future events.  I will share both the scientific meaning of the discovery and some of the personal stories behind it.

It was in April 1986 when Bednorz and Mueller of the IBM Zürich laboratories sent a paper about “possible high-Tc superconductivity” to Zeitschrift für Physik B.  The resulting bombshell changed condensed-matter physics forever.  Experimenters and theorists developed methods to measure and calculate in ways that were much improved over prior years. However, despite 30 years of intense study, the description of these materials remains incomplete. I’ll discuss the  discovery of the high Tc cuprates from the perspective of a participant.  I’ll then turn to what infrared spectroscopy can tell us about their properties. Measurements for a number of cuprate families of optical reflectance over a wide spectral range (far-infrared to ultraviolet) have been analyzed using Kramers-Kronig analysis to obtain the optical conductivity, s(w), and (by integration of the real part of the conductivity) the spectral weight of low- and mid-energy excitations. For the Kramers-Kronig analysis to give reliable results, accurate high-frequency extrapolations, based on x-ray atomic scattering functions, were used. When the optical conductivities of the normal and superconducting states are compared, a transfer of spectral weight from finite frequencies to the zero-frequency delta-function conductivity of the superconductor is seen. The strength of this delta function gives the superfluid density, rs. There are two ways to measure rs, using either the low energy spectral weight or by examination of the imaginary part, s2(w); both estimates show that 98% of the ab-plane superfluid density comes from low energy scales, below about 0.15 eV. Moreover, there is a notable difference between clean metallic superconductors and the cuprates.  In the former, the superfluid density is essentially equal to the conduction electron density. The cuprates, in contrast, have only about 20% of the ab-plane low-energy spectral weight in the superfluid. The rest remains in finite-frequency, midinfrared absorption. In underdoped materials the superfluid fraction is even smaller. The consequences of this observation for the electronic structure will be addressed.

Films of semiconductor nanocrystals are used as a novel, low-cost electronic materials for optoelectronic devices. To achieve their full potential a better understanding of their conductivity as a function of concentration of donors is required. So far, it is not known how many donors will make a nanocrystal film metallic. In bulk semiconductors, the critical concentration of electrons at the metal-insulator transition is universally described by the famous Mott criterion. We show theoretically that in a dense NC film, where NCs touch each other by small facets with radius r << d, the critical concentration of electrons N at the metal-insulator transition satisfies the condition is given by N r^3 = 1.
This critical concentration is typically 100 times larger than the Mott one. In the accompanying experiments, we investigate the conduction mechanism in films of phosphorus-doped silicon nano-crystals. At the largest electron concentration achieved in our samples, which is half the predicted N, we find that the localization length of hopping electrons is close to three times the nano-crystals diameter, indicating that the film approaches the metal-insulator transition.

The motion of molecules across channels and pores is critically important for understanding mechanisms of many biological, chemical, physical and industrial processes. Here we investigate the role of different types of interactions in the channel-facilitated molecular transport by analyzing exactly solvable discrete-state stochastic models. According to this approach, the channel transport is a non-equilibrium process that can be viewed as a set of coupled quasi-chemical transitions between discrete spatially separated states. It allows us to obtain a full dynamic description of the translocation via the pore, clarifying many aspects of these complex processes. We show that the strength and the spatial distribution of the molecule/channel interactions can strongly modify the particle fluxes through the system. Our analysis indicates that the most optimal transport is achieved when the binding sites are near the entrance or near the exit of the pore, depending on the sign of the interaction potentials. These observations allow us to explain current single-molecule experiments on the translocation of polypeptides through biological channels. We also suggest that the intermolecular interactions during the channel transport might significantly influence the overall translocation dynamics. Our explicit calculations show that the increase in the flux can be observed for some optimal interaction strengths. But the flux can also be fully suppressed for some conditions. The relevance of these results for biological systems is discussed. The physical-chemical mechanisms of these phenomena are analyzed from the microscopic point of view.

Many complex phenomena are so familiar that we hardly realize that they defy our normal intuition.  Examples include the anomalous flow of granular material, the long messy tendrils left by honey spooned from one dish to another, the pesky rings deposited by spilled coffee on a table after the liquid evaporates or the common splash of a drop of liquid onto a countertop.  Aside from being uncommonly beautiful to see, many of these phenomena involve non-linear behavior where the system is far from equilibrium.  Although most of the world we know is beyond description by equilibrium theories, we are still only at the threshold of learning how to deal with such deep and complex behavior.  Thus, these are phenomena that can lead the inquisitive into new realms of physics.

Detection of distant quasars at redshifts of ~6-7 provides a challenge to the standard picture of structure formation in the universe within the hierarchical framework, as the universe is less than a Gigayear old at this time. What are seeds of supermassive black holes (SMBHs) that power these luminous objects? After all,  massive objects should form late in the evolution ...  Did  SMBHs form as a result of stellar evolution? In my talk, I will address various aspects of this problem and discuss viable and emerging alternatives to this paradigm.

At NIST, we have the enjoyable jobs of combining i) state-of-the-art research with ii) the fascinating search for higher and higher accuracy measurements.  In this talk, I will i) introduce the SI system of units and explain why devices that can move around single electrons one-by-one are of great interest, ii) give an introduction to the nanoelectronic devices known as single electron transistors and pumps, iii) describe a high-accuracy measurements of the charge of electrons in a metal, and iv) discuss the possibility that this charge is not the same as the charge of a free electron in vacuum.

Magnetism has been an old subject dating back to antiquity.  Few could envision that modern magnetism would enter a golden era with the realization of so many new phenomena and game-changing technologies.  These remarkable advances are due to spin ½ of electrons, as illustrated in this talk through several recent examples, including pure spin current phenomena, skyrmion materials, and p-wave superconductivity.

On July 14, 2015, New Horizons, an interplanetary space probe, flew by Pluto, capturing the first high resolution photographs of Pluto’s surface and atmosphere. New Horizons data has revealed stunning geology including ice volcanoes, Nitrogen ice glaciers, mysterious internal heating, and the “snakeskin” patterns among 50 other discoveries. UVA’s planetary astronomer, Anne Verbiscer, will describe Pluto’s amazing science phenomena, and Alice Bowman will explain the missions and engineering side of New Horizons sharing her experience as New Horizons’ MOM. This event is meant for the general public, and everyone is invited. A reception will follow the talk.

Sponsored by UVA Physics and Astronomy Departments.
Organized by Astronomical Society at UVA and SPS

A map showing the location of Maury Hall is available online at the following address:
http://www.virginia.edu/webmap/popPages/55-MauryHall.html

Atom interferometry, in which de Broglie waves of matter are coherently split and later recombined to make interference fringes, is a precision measurement method with applications in many fields of physics.  In Arizona, we measured the ground-state static electric-dipole polarizabilities of Cs, Rb, and K atoms with 0.2% uncertainty using an atom beam interferometer.  We also measured a tune-out wavelength for K atoms with sub-picometer uncertainty.  I will discuss how these experiments use electric field gradients to induce polarizability-dependent phase shifts for atomic de Broglie waves. Our measurements provide benchmark tests for atomic structure calculations and thus test the underlying theory used to predict van der Waals forces and to interpret atomic parity non-conservation experiments.

Machine Learning (statistical engineering) capabilities are in a phase of tremendous growth. Underlying these advances is a strong and deep connection to various aspects of statistical physics. There is also a great opportunity in pointing these tools toward physical modeling. In this colloquium I  illustrate the two-way flow of ideas between physics and statistical engineering on three examples from our team LANL. First, I review the work on  structure learning and statistical estimation in power system distribution (thus physical) networks. Then I describe recent progress in constructive understanding of graph learning (on example of inverse Ising model) illustrating that the generic inverse task (of learning) is computationally easy in spite of the fact that the direct problem (inference or sampling) is difficult. I conclude speculating how macro-scale models of physics (e.g. large eddy simulations of turbulence) can be learned from micro-scale simulations (e.g. of Navier-Stocks equations).

https://sites.google.com/site/mchertkov/

The emergent universality in the nonlinear magnetic response of itinerant metamagnets will be discussed. Recent experimental work on heavy fermions, Hunds metals, and single molecule magnets will be presented. The appeal of the ‘single energy scale model’ developed in the context of these new measurements [(a) "Universality in the Nonlinear Magnetic Response of Strongly Correlated Metals", B.S. Shivaram, D.G. Hinks, M.B. Maple and P. Kumar, Phys. Rev., B89, 241107(Rapid Communication), 2014. [b] "Metamagnetism and the Fifth Order Susceptibility in UPt3", B.S. Shivaram, Brian Dorsey, D.G. Hinks and Pradeep Kumar, Phys. Rev., B89, 161108(Rapid Communication), (2014). [c] “High Field Ultrasound Measurements in UPt3 and the Single Energy Scale Model of Metamagnetism”, B.S. Shivaram, V.W. Ulrich, P. Kumar and V. Celli, Phys. Rev.B, 91, 115110, 2015] will be critically examined.

Single-layer of molybdenum disulfide (MoS₂) and other transition metal dichalcogenides appear to be promising materials for next generation nanoscale applications (optoelectronic and catalysis), because of their low-dimensionality, intrinsic direct band-gap which typically lies in the visible spectrum, and strikingly large binding energies for excitons and trions. Several experimental groups have already reported novel electronic and transport properties which place these material beyond graphene for device applications. MoS₂ is also known to be a leading hydrodesulphurization catalyst. Efforts are underway to further tune these properties through alloying, defects, doping, coupling to a substrate, and formation of bilayer stacks (homo- and hetero-structures).  In this talk I will present results [1-3] which provide a framework for manipulating the functionality of these fascinating materials and take us closer to the goal of rational material design.  My emphasis will be on properties of pure and defect-laden single layer MoS₂ with and without underlying support.  I will also provide rationale for the differences in the excitation energetics and ultrafast charge dynamics in single and bilayer (hetero and homo) dichalcogenides.

[1] D. Sun, et al., “An MoSx Structure with High Affinity for Adsorbate Interaction,” Angew. Chem. Int. Ed. 51, 10284 (2012).

[2] D. Le, T. B. Rawal, and T. S. Rahman, “Single-Layer MoS₂ with Sulfur-Vacancies: Structure and Catalytic Application,” J. Phys. Chem. C 118, 5346 (2014).

[3] A. Ramirez-Torres, V.Turkowski, and T. S. Rahman, “Time-dependent density-matrix functional theory for trion excitations: application to monolayer MoS2,” Phys. Rev. B 90, 085419 (2014).

I will review the basic underlying science of climate and climate change, including physically-based models of Earth's climate. I will motivate the use of a simple, zero-dimensional "Energy Balance Model" of Earth's radiative balance that can be used to estimate the global mean surface temperature of Earth. I will show how this model successfully reproduces the observed historical changes in global temperature, and how it can be used to assess various questions about future human-caused climate change.

The very successful Run I of the Large Hadron Collider (LHC) culminated in the discovery of the Higgs boson which was the subject of the 2013 Nobel Prize.

How will we know if there are other "undiscovered" particles in the data? (And, was there a hint from CERN last month???)  This will require improved calculations, and the key ingredients are:

i) higher-order theoretical cross section calculations, and

ii) precise Parton Distribution Functions (PDFs) that characterize the proton structure.

Surprisingly, these predictions are influenced by a wide range of data including precision low-energy nuclear results. Recent theoretical developments improve our ability to address the QCD multi-scale problem and higher orders across the full kinematic range.

We look at some of the topics, puzzles, and challenges that lie on the horizon, and identify areas where additional efforts are required.

Quantum computing offers revolutionary promises of scientific and societal importance, based on its exponential speedup of particular tasks: on the one hand, Richard Feynman's quantum simulator would allow us to tackle currently intractable quantum chemistry problems (nitrogen fixation, carbon sequestration) as well as quantum physics ones (high-Tc superconductivity); on the other hand, Peter Shor's algorithm for factoring integers would render RSA encryption obsolete.

Building a practical quantum computer demands that one address the challenges of decoherence and scalability. While the platforms of trapped-ion qubits and of superconducting qubits have made spectacular progress in the fight against decoherence, our approach has been to tackle scalability, in particular by discovering a new “top down,” rather than “bottom up,” method for generating the entangled states, or "cluster" states, that enable the particular flavor of quantum computing called measurement-based, or one-way, quantum computing.  

Our method uses the continuous variables of light — “qumodes,” rather than qubits — defined by the quadrature amplitudes of the quantized electromagnetic field emitted over the cavity modes, or quantum optical frequency comb, of a single optical parametric oscillator. We demonstrated a world-record cluster state size of 60 entangled qumodes (3 × 103 in progress), all simultaneously available in the frequency domain. I will also present our new proposal for generating cluster states of unlimited size by using both the time and frequency degrees of freedom.

For many years, it was generally thought that spatial imaging of the proton was impossible in principle, due to the relativistic recoil of the proton when ever it is probed at momentum scales of order of the inverse of the proton size.  Two decades ago, a new set of QCD matrix elements were defined, called Generalized Parton Distributions (GPDs), that encode the spatial distributions of quarks and gluons transverse to a preferred momentum axis.  It was independently discovered that the GPDs are accessible experimentally in Deep Virtual Exclusive reactions:  high energy reactions of the type e p —> e p gamma.

I will review the progress of experimental efforts to measure GPDs, and discuss the extent to which spatial distributions can be extracted from present and future data.

Matter-antimatter asymmetry is one of the most outstanding mysteries of the universe that provides a necessary condition to our own existence. There have been various attempts to solve this mystery including 'Baryogenesis' hypothesis. However, the B-factory experiments during the last decade showed that the observed CP-violation (CPV) in the quark sector is not big enough for baryogenesis to be a viable solution to the matter-antimatter asymmetry. This leads us to the 'Leptogenesis' hypothesis, in which CPV in the lepton section plays a crtical role to create the matter-antimater asymmetry at the onset of the Big Bang. Thus, experimental observation of CPV in the lepton sector could prove to be tantamount to one of the most important discoveries in our understanding of the universe.

In 2011, the T2K experiment published a result that provided the first indication for a non-zero $\theta_{13}$, the last unknown mixing angle in the lepton sector at that time, at 2.5 sigma level of significance. In 2013, after analyzing two more years of data taken since 2011, the experiment reported "Observation of electron neutrino appearance from a muon neutrino beam" at 7.3 sigma level of significance. While neutrino oscillation has been well-established since the discovery by the Super-Kamiokande experiment in 1998, there have not been a definitive observation of neutrino oscillation in a so-called "appearance mode", and this new T2K observation is the first time an explicit neutrino flavor (electron) appearance is observed from another neutrino flavor (muon). This observation also opens the door to study CPV in neutrinos. When incorporating recent precision measurements on $\theta_{13}$ by the reactor experiments along with other neutrino oscillation parameter measurements, T2K data show an intriguing initial result on the $\delta_{CP}$, which is further corroborated by the Super-Kamiokande atmospheric neutrino results as well as the most recent results from NOvA.

Ultimately, however, in order to establish unequivocal results on leptonic CPV, we need a next generation experiment with a more powerful beam, and a larger and/or higher resolution detector. The Deep Underground Neutrino Experiment (DUNE) in US that is newly established as a truly international collaboration, is such an experiment. Physics goals of DUNE include: discovery of CPV in the lepton sector, detrmination of mass hierarchy, discovery of proton decay and observation of neutrinos from the Type-II supernovae. In this talk I will introduce the rapidly developing DUNE experiment and the collaboration, and also discuss possible opportunities for participation.

I will also briefly comment on the Nobel Prize in Physics 2015 as well as The Breakthrough Prize in Fundamental Physics 2016 that were given to the
neutrino oscillation experiments.

Studies of the fundamental origins of friction have undergone rapid progress in recent years with the development of new experimental and computational techniques for measuring and simulating friction at atomic length and time scales.  The increased interest has sparked a variety of discussions and debates concerning the nature of the atomic-scale and quantum mechanisms that dominate the dissipative process by which mechanical energy is transformed into heat.  Measurements of the sliding friction of physisorbed monolayers and bilayers in gaseous and liquid enviroments provide information on the relative contributions of electronic, magnetic, electrostatic and phononic dissipative mechanisms. The experiments will be discussed within the context of current theories of how friction originates at the atomic scale.

Friction affects many aspects of everyday life and has played a central role in technology dating from the creation of fire by rubbing sticks together to current efforts to make nanodevices with moving parts. The friction "laws" we teach today date from empirical relationships observed by da Vinci and Amontons centuries ago. However, understanding the microscopic origins of these laws remains a challenge. While Amontons said area was proportional to load and independent of area, most modern treatments assume that friction is proportional to the real area of contact where atoms on opposing surfaces are close enough to repel. Calculating this area is complicated because elastic interactions are long range and surfaces are rough on a wide range of scales. In many cases they can be described as self-affine fractals from nanometer to millimeter scales. The talk will first show that this complex problem has a simple solution. Dimensional analysis implies a linear relation between real contact area and load that can explain both Amontons' laws and many exceptions to them. Next the talk will explain why we can't climb walls like spiderman even though the attractive interactions between atoms on our finger tips should provide enough force to support our weight. The talk will conclude by considering how forces in the contact area give rise to friction. Friction shows surprisingly counterintuitive and complex behavior in nanometer to micrometer scale contacts and only a few explanations are consistent with macroscopic measurements.

Until about 2005, molecular rotational spectroscopy was performed using narrowband (~1 MHz) excitation of a low-pressure gas in a resonant cavity.  This method offers high sensitivity for each data acquisition, but the time required to perform a spectrum scan over about 10 GHz, needed to capture the rotational spectrum, was a major limitation to applications of the technique.  Advances in high-speed digital electronics have made it possible to design spectrometers that offer instantaneous, broadband (> 10 GHz) performance.  During our initial work with high-speed arbitrary waveform generators and digitizers (with Tom Gallagher) we developed the method of chirped pulse Fourier transform rotational spectroscopy that uses a pulse with linear chirp to phase-reproducibly excite the gas sample.  The subsequent coherent emission (free induction decay) is detected with the high-speed digitizer and the frequency domain spectrum is obtained using FFT analysis.  Since the introduction of the technique in 2008 [1], the method has been applied to unimolecular reaction dynamics [2], the structures of molecular clusters [3], and the laboratory identification of molecules in the interstellar medium [4].  The technique has been extended to mm-wave spectroscopy with applications to Rydberg spectroscopy [5], chemical reaction dynamics, and analytical chemistry.  The broadband technique has also enabled a new generation of molecular structure studies in the field of chirality [6] with the potential for solving significant challenges for real-time pharmaceutical manufacturing.

References

[1] G.G. Brown, B.C. Dian, K.O. Douglass, S.M. Geyer, and B.H. Pate, “A Broadband Fourier Transform Microwave Spectrometer Based on Chirped Pulse Excitation” Rev. Sci. Instrum. 79, 053103 (2008).

[2] B.C. Dian, G.G. Brown, K.O. Douglass, and B.H. Pate, “Measuring Picosecond Isomerization Dynamics via Ultra-broadband Fourier Transform Microwave Spectroscopy”, Science 320, 924-928 (2008).

[3] C. Pérez, M.T. Muckle, D.P. Zaleski, N.A. Seifert, B. Temelso, G.C. Shields, Z. Kisiel, and B.H. Pate, “Structures of Cage, Prism, and Book Isomers of Water Hexamer from Broadband Rotational Spectroscopy”, Science 336, 897-901 (2012).

[4] D.P. Zaleski, N.A. Seifert, A.L. Steber, M.T. Muckle, R.A. Loomis, J.F. Corby, O. Martinez, Jr., K.N. Crabtree, P.R. Jewell, J.M. Hollis, F.J. Lovas, D. Vasquez, J. Nyiramahirwe, N.  Sciortino, K. Johnson, M.C. McCarthy_, A.J. Remijan, and B.H. Pate, “Detection of E-cyanomethanimine towards Sagittarius B2(N) in the Green Bank Telescope PRIMOS Survey”, Ap. J. Letters, 765, L10 (2013).

[5] K. Prozument, A.P. Colombo, Y. Zhou, G.B. Park, V.S. Petrovic, S.L. Coy, and R.W. Field, “Chirped-pulse Millimeter-wave Spectroscopy of Rydberg-Rydberg Transitions”, Phys. Rev. Lett. 107, 143001 (2011).

[6] D. Patterson, M. Schnell, and J.M. Doyle, “Enantiomer-specific detection of chiral molecules via microwave spectroscopy”, Nature 497, 475 (2013).

The National Academy of Engineering has identified 14 Grand Challenges for Engineering for the 21st Century, spanning human needs from sustainability to security, health and joy of living.  The last category includes such topics as engineering the tools of scientific discovery. This talk will include a brief review of the NAE Grand Challenges and the response of higher education to the Challenges, and will conclude with a review of one Grand Challenge topic:  the development of ultra-compact particle accelerators based on surfing at (nearly) the speed of light on waves created by lasers or particle beams in a plasma gas. The prospects of these devices as tools of scientific discovery as well as beam therapy will be discussed.

Understanding Magnetism is a complex undertaking: it relies on our knowledge of the exact position of magnetic ions in a crystal and their interactions. More important, at its core, this is fundamentally a quantum problem and requires understanding the cooperative effects of many degrees of freedom. In the past decade, we have witnessed enormous progress in experiments that consist of placing magnetic atoms at predetermined positions on substrates, and building magnetic nanostructures, one atom at a time. The electrons in the substrate mediate the interactions between the spins, and scanning tunneling microscopy allows one to study their properties.

In order to understand these interactions, we rely on a theory developed decades ago by Ruderman, Kittel, Kasuya, and Yosida, dubbed "RKKY Theory", which applies when the spins are classical. The quantum nature of the electronic spin introduces more complexity, and competition with another quantum phenomena: the Kondo effect. The combined effect is non-trivial, and can only be studied by numerical means.  I will describe this effect by introducing an exact mapping onto an effective one-dimensional problem that we can solve with the density matrix renormalization group method (DMRG). I will also show that for dimension d>1, Kondo physics dominates even at short distances, while the ferromagnetic RKKY state is energetically unfavorable. This may have important implications for our understanding of heavy fermion materials and magnetic semiconductors.

I will review the current status of the Mu2e and NOvA experiments at Fermilab.  These experiments hope to shed light on several important topics in particle physics:  neutrino oscillations, lepton flavor, the matter/antimatter asymmetry of the Universe, dark matter, and others.   As I describe the status and goals of these experiments I will highlight the impact of our UVA efforts. 

When magnetic moments are interacting with each other in a situation resembling that of complex love triangles, called frustration, a large set of states that are energetically equivalent emerge. This leads to exotic spin states such as spin liquid and spin ice. In their paper recently published in the Proceedings of the National Academy of Sciences (PNAS), we presented evidence for the existence of a topological glassy state, that we call a spin jam, induced by quantum fluctuations. The case in point is SrCr9pGa12-9pO19 (SCGO(p)), a highly frustrated magnet, in which the magnetic Cr ions form a quasi-two-dimensional triangular system of bi-pyramids. This system has been an archetype in search for exotic spin states. Understanding the nature of the state has been a great intellectual challenge. Our new experimental data and theoretical spin jam model provide for the first time a coherent understanding of the phenomenon. Furthermore, the findings strongly support the possible existence of purely topological glassy states.

I will survey a number of exciting new developments in hadron physics.

These include: new insights into the nature of the color-confining confinement quark potential in quantum chromodynamics; a novel application of supersymmetry to hadron physics; the relation between the parameter Λ_MS which controls high-energy interactions of quarks to the mass of the proton; and the elimination of the renormalization scale ambiguity for perturbative QCD calculations.

I will also discuss several novel experimental tests of QCD which can be performed at JLab, including: hard exclusive and diffractive reactions, flavor-dependent antishadowing of nuclear interactions; intrinsic strange- and charm-quark phenomena; the production of tetraquarks and other exotic hadronic states; and factorization-breaking lensing phenomena.

Molecules cooled to ultralow temperatures provide fundamental new insights to strongly correlated quantum systems, molecular interactions and chemistry in the quantum regime, and precision measurement.  Complete control of molecular interactions by producing a molecular gas at very low entropy and near absolute zero has long been hindered by their complex energy level structure. Recently, a range of scientific tools have been developed to enable the production of molecules in the quantum regime. Here, molecular collisions follow full quantum descriptions.  Chemical reaction is controlled via quantum statistics of the molecules, along with dipolar effects. Further, molecules can be confined in reduced spatial dimensions and their interactions precisely manipulated via external electromagnetic fields.  For example, by encoding a spin-1/2 system in rotational states, we realize a spin lattice system where many-body spin dynamics are directly controlled by long-range and anisotropic dipolar interactions. These new capabilities promise further explorations of strongly interacting and collective quantum effects in exotic quantum matter.

Inflationary cosmology gives a plausible explanation for many observed features of the universe, including its uniformity, its mass density, and the patterns of the ripples that are observed in the cosmic microwave background. Beyond what we can observe, most versions of inflation imply that our universe is not unique, but is part of a possibly infinite multiverse. I will describe the workings of inflation, the evidence for inflation, and why I believe that the possibility of a multiverse should be taken seriously.

As Chancellor of the Pyongyang University of Science & Technology (PUST) starting in October, 2010, I have seen the slow changes in DPRK, especially after Kim Jong Un took over the power in January, 2012. Globalizing DPRK is essential for peaceful coexistence and eventual reunification of two Koreas. One way to achieve this goal is Science Diplomacy, in particular educating young talents and globalizing them.

In this colloquium, a brief introduction about collaborative activities in science and technology between South and North Koreas will be presented, followed by more extensive presentation about the history and current status of PUST. And then the globalization efforts of PUST will be presented, to show that the PUST students are being internationalized and it is hoped that they will globalize their country in the near future, which will make an important contribution to the World Peace.

Cosmic rays which encounter the Earth's atmosphere produce showers of muons and high-energy photons, which can be detected using a smartphone camera. The CRAYFIS experiment was devised to observe cosmic rays at ultra-high energy (UHE) using the existing network of smartphones as a ground detector array. We'll describe our custom app, our lab measurements of smartphone efficiency, and our latest projections for the sensitivity of the CRAYFIS array to UHE cosmic rays.

The boundary between metal and insulator remains a fruitful source of emergent phenomena in materials, ranging from oxides, to cold atoms. Typically the insulating side of this boundary is occupied by an electronic crystal (though often disordered), and at higher temperatures a polaronic liquid or bad metal. While the paradigm Hamiltonian for this transition involves only short –range electronic correlations, in practice the transition is tuned by disorder, by screening of longer range Coulomb forces, and by coupling to the lattice.  These lectures will discuss a few of these phenomena in real oxide systems including bulk and interface transition metal oxides.

Heterostructure oxides offer the opportunity to build in electric fields by precise control of chemistry on the atomic scale, used recently to generate modulation doping of two- dimensional electron gases (2DEG) in oxides. The origin of the 2DEG, whether in pristine or defected materials, is under debate. I will discuss the role of surface redox reactions, in particular O vacancies, as the source of mobile carriers, and also discuss their role in the switching of ferroelectricity in ultra-thin films.

While electric charges can be screened by mobile carriers, the same is not true of strain fields, which have intrinsic long-range interactions that cannot be screened. When strain fields are produced as a secondary order parameter in phase transitions - as for example in ferroelectrics - this produces unexpected consequences for the dynamics of order parameter fluctuations, including the generation of a gap in what would otherwise have been expected to be Goldstone modes. In some cases, eg manganites and nickelates, other intra-cell modes can nonlinearly screen the order parameter, which produces a strong sensitivity of ordering to octahedral rotations, essentially a jamming transition. This is relevant for tuning entropic effects at phase transitions, perhaps to enhance electro-caloric effects.

Notions of geometry, topology, and dimensionality have directed the historical development of quantum-gas physics, as has a relentless search for longer-lived matter-wave coherence and lower absolute temperature. With a toolbox of forces for confinement, guiding, and excitation, physicists have used quantum gases to test fundamental ideas in quantum theory, statistical mechanics, and in recent years notions of strongly-correlated many-body physics from the condensed-matter world.  Some of this work has been hampered by terrestrial gravity; levitation schemes of varying degree of sophistication are available, as are atomic-fountain and drop-tower microgravity facilities, but the long-term free-fall environment of low-Earth orbit remains a tantalizing location for quantum-gas experiments.

I will review a planned NASA microgravity program set to launch to the International Space Station in 2016. One set of experiments will explore a trapping geometry for quantum gases that is both theoretically compelling and difficult to attain terrestrially: that of a spherical or ellipsoidal shell. This trap could confine a Bose-Einstein condensate to the surface of an experimentally-controlled “bubble.” Other experiments will focus on atom interferometry and few-body physics. I will also review recent terrestrial work tailoring periodic geometries for BEC toward interesting solid-state analogues.

The non-interacting topological insulators (TIs) have attracted great interest in the last decade. While this class of materials is today well-understood, the effect of electron-eletron interactions in such systems remains in general elusive. In this talk, I will address two different aspects of interactions in 2D topological band structures: (i) in some cases, strongly interacting TI models can be used to describe the exotic magnetic properties of certain transition metal oxides. (ii) in other cases, strong interactions can drive a TI into spin-liquid phases.

The Standard Model of strong and electroweak interactions, together with Einstein's theory of general relativity, provide the basis for the highly successful hot big bang cosmology. A large quantity of groundbreaking cosmological observations favor an epoch of primordial inflation, during which the very early universe experienced an exponentially rapid expansion phase before transitioning to a hot, radiation dominated ('big bang') phase. The present universe, it is now widely accepted, is largely dominated by dark energy, whose nature is entirely mysterious, and also by dark matter, presumably consisting of some relic and still undetected elementary particle.

Some aspects of inflationary cosmology will be reviewed, including its prediction concerning the existence of primordial gravity waves whose discovery would have profound implications for high energy physics and cosmology.

Recently there has been great progress in realizing platforms for topological quantum computation, with mounting evidence of the experimental observation of Majorana zero modes. However, braiding such zero modes does not yield a set of transformations sufficient to perform universal, fault tolerant computation. One way forward is to engineer systems realizing Z3 parafermion zero modes, which generalize Majorana zero modes. Coupled Z3 parafermions could hybridize into a phase supporting bulk Fibonacci anyons, a type of non-Abelian anyon that does have universal braiding statistics. 

Using the density matrix renormalization group (DMRG), we study a two-dimensional model of coupled Z3 parafermions. By working close to the weakly-coupled chain limit, we are able to identify the Fibonacci phase on cylinders as small as four sites in circumference then track its evolution, finding it survives even to the isotropic limit of our model on larger cylinders. We examine the extent of this phase and the wider phase diagram of our model, which turns out to harbor a second topological phase.