# Atomic Physics Seminars

Atomic
Monday, November 18, 2019
4:00 PM
Physics Building, Room 204

## "Dynamical phases and transitions in an ultracold Fermi gas"

Scott Smale , University of Toronto
[Host: Cass Sackett]
ABSTRACT:

Non-equilibrium systems are ubiquitous in nature. They are actively studied in a wide range of fields, from biological cell membranes to city traffic planning. For the past several years our lab has been studying the dynamics of non-equilibrium ultracold degenerate Fermi gasses. We probe the dynamics via fast radio-frequency pulses enabled by trapping the atoms close to a microfabricated chip. The kinds of dynamics we have probed include the diffusion of spin in a strongly interacting Fermi gas, the rise of correlations in the gas after a quench of the interaction strength, and the phase transition between two different dynamical phases. Dynamical phases and the transitions between them are one possible framework to extend the powerful ideas of equilibrium statistical mechanics to diverse non-equilibrium systems. In my talk I will discuss our work on dynamics, focussing on our recent observation of dynamical phase transitions in the collective Heisenberg spin model.

Atomic
Monday, November 11, 2019
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Quantum-classical hybrid algorithms with trapped ions"

Norbert Linke , Joint Quantum Institute/University of Maryland
[Host: Peter Schauss]
ABSTRACT:

We present results from a programmable quantum computer comprised of a chain of individually trapped 171Yb+ ions. It features individual laser beam addressing and individual readout, and can be configured to run any sequence of single- and two-qubit gates [1]. We combine this setup with different classical optimization routines to implement a so-called hybrid system. Quantum-classical hybrid protocols offer a path towards the application of near-term quantum computers for different optimization tasks. They are attractive since part of the effort is outsourced to a classical machine resulting in shallower and narrower quantum circuits, which can be executed with lower error rates.
We have realized several experimental demonstrations relating to this approach, such as the training of shallow circuits for Generative Modeling using a Bayesian optimization routine [2], tackling the Max-Cut problem using the Quantum Approximate Optimization Algorithm (QAOA) [3], and the preparation of thermal quantum states [4].
Recent results, limitations of the above methods, and ideas for boosting these concepts for scaling up the quantum-classical hybrid architecture will be discussed.
[1] S. Debnath et al., Nature 563:63 (2016); [2] D. Zhu et al., Science Advances 5, 10 (2019); [3] O. Shehab et al., arXiv:1906.00476 (2019); [4] D. Zhu et al., arXiv:1906.02699 (2019)

SLIDESHOW:
Atomic
Monday, November 4, 2019
4:00 PM
Physics Building, Room 204

## "Quantum spins in space: the rich phases of spinor Bose gases"

Raman Chandra , Georgia Tech
[Host: Peter Schauss]
ABSTRACT:

Many-body quantum systems have come under intense focus in recent years to enable a number of quantum simulation and sensing tasks.  Neutral atoms, ions and solid state qubits have all emerged as key platforms for inquiry.  One key set of questions concerns the ability of these delicately tailored quantum systems to relax to equilibrium when they are isolated from the environment, and whether such dynamics might have universal features.  Research in our laboratory on magnetic quantum fluids comprised of spin-1 Bose-Einstein condensed atoms (BECs) has a remarkable potential to address this problem.  In this talk I will show data from our lab demonstrating the rich interplay between many actors--magnetic interactions between spins, the influence of external magnetic fields, and the spatial quantum dynamics of many interacting modes that all compete to determine the non-equilibrium behavior.

Dr. Raman Biosketch:  Dr Chandra Raman is Associate Professor in the School of Physics at Georgia Tech where he performs experimental research on ultracold atomic gases and builds miniature atomic systems for quantum sensing applications. His work aims to understand the basic physics of complex quantum systems to harness them for applications. His group at Georgia Tech has uncovered new properties of quantized vortices, spin textures and quantum phase transitions in ultracold Bose gases, work for which he was awarded Fellowship in the American Physical Society in 2013. From 2013-15 he took a leave of absence to work in industry to better understand real world atomic sensors, work which he has translated into his laboratory today.

Atomic
Thursday, October 31, 2019
11:00 AM
Physics Building, Room 204
Note special date.
Note special time.

## "Off-resonant RF Heating of Ultracold Plasmas to Measure Collision Rates "

John Guthrie , Colorado State University
[Host: Cass Sackett]
ABSTRACT:

Ultracold plasmas provide us an opportunity to study exotic plasma regimes on a table-top laboratory scale. In particular, we can explore parameter spaces where strong coupling and electron magnetization effects play an important role like in some fusion and astrophysical systems. We have developed a new technique to measure electron-ion collision rates in ultracold plasmas using off-resonant RF heating of the electrons. By using the known variation in photoionization energy with photoionization laser wavelength and applying controlled sequences of electric fields, the amount of heating imparted can be calibrated and precisely measured. This allows the comparison of electron-ion collision rates as a function of plasma parameters such as electron temperature/degree of strong coupling and magnetization. A description of this technique and the experimental results obtained with it will be presented.

Atomic
Monday, October 28, 2019
3:30 PM
Online, Room via Zoom
Note special time.
Note special room.

## "Dynamics of quantum systems with long-range interactions"

Alexey Gorshkov , Joint Quantum Institute/University of Maryland
[Host: Peter Schuass]
ABSTRACT:

Atomic, molecular, and optical systems often exhibit long-range interactions, which decay with distance r as a power law 1/r^alpha. In this talk, we will derive bounds on how quickly quantum information can propagate in such systems. We will then discuss applications of these bounds to numerous phenomena including classical and quantum simulation of quantum systems, prethermal phases in Floquet systems, entanglement area laws, sampling complexity, and scrambling.

Atomic
Monday, October 21, 2019
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Path to building quantum spin liquids and topological qubits within existing quantum hardware"

Dmitry Green , AppliedTQC.com, ResearchPULSE LLC
[Host: Peter Schauss]
ABSTRACT:

We address a central problem in the creation and manipulation of quantum states: how to build topological quantum spin liquids with physically accessible interactions. Theorists have been studying models of quantum spin liquids that rely on "multi-spin" interactions since the 1970s, and, more recently, have realized that these models can be used for quantum computing. However, nature does not provide such interactions in real materials. We construct a lattice gauge model where the required, fully quantum, multi-spin interactions can in fact be emulated exactly in any system with only two-body Ising interactions plus a uniform transverse field. The latter systems do exist. Therefore, our solution is an alternative path to building a workable topological quantum computer within existing hardware.  Our bottom-up construction is generalizable to other  gauge-like  theories,  including  those  with  fractonic  topological  order  such  as the  X-cube model. Taken as a whole, our approach is a blueprint to emulate topologically ordered quantum spin liquids in programmable quantum machines.

SLIDESHOW:
Atomic
Wednesday, May 8, 2019
11:00 AM
Physics Building, Room 204
Note special date.
Note special time.

## "Cold atom gravimetry with atom interferometry: advances in technology at ANU and progress towards applications."

John Close , Australian National University
[Host: Cass Sackett]
ABSTRACT:

I will discuss the cold atom gravimetry program at ANU. I will talk about our program in field deployed devices in broad terms and programs we are pursuing in squeezing and advanced detection methods.. I will also discuss our program to model and design fit for purpose cold atom gravimeters and accelerometers  for a variety of applications in Earth science, mineral exploration, hydrology and inertial navigation.

Atomic
Monday, April 29, 2019
11:30 AM
Physics Building, Room 313
Note special time.
Note special room.

## "Simulations and Designs of Atom Chip Apparatus for BEC Interferometry"

Zhe Luo , University of Virginia - Physics
[Host: Cass Sackett]
ABSTRACT:

A Sagnac interferometer using Bose-Einstein condensates for rotation sensing is implemented in a harmonic trapping magnetic potential. The trapped cold atom cloud is manipulated by standing wave laser beams to produce two reciprocal interferometers. They provide common-mode rejection of accelerations, trap fluctuations and other noise sources while the Sagnac phase is differential between two interferometers. An image processing program is being developed to quickly extract positions and sizes of atom packets from their trajectories. Besides, a new atom chip is designed and constructed based on double layer spiral copper wires with different chirality. A supporting chamber for testing the atom chip is also designed and used to adjust trapping frequencies and allow laser beams coming through. The ultimate goal is to realize a compact and portable microchip-based atom gyroscope for rotation sensing and inertial navigation.

Atomic
Monday, April 29, 2019
3:00 PM
Mechanical & Aerospace Engineering Building, Room 346
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## "A variational approach for phase transition in interacting electron-phonon system"

Yuan Liang , University of Virginia - Physics
ABSTRACT:

We employ a variational approach by optimizing the free energy of an anharmonic Hamiltonian with respect to strain tensor, interatomic coordinates and force constants in an interacting electron-phonon system. The goal is to predict possible phase transitions in crystal structures at finite temperatures. The variational method is based on Bogoliubov inequality to get an approximation to the Helmholtz free energy in a lattice with anharmonic potential energy terms. A harmonic trial Hamiltonian is used for the minimization. The optimization will give the set of equations corresponding to atomic displacements, lattice strain, IFCs and other order parameters, leading to phonon frequencies at each k-point for every temperature. The reliability of the approach is then checked in 1D/3D cases, comparing to available computational/experimental results and by applying DFT method to compute free energies of various phases at different temperatures.

Atomic
Monday, April 29, 2019
3:30 PM
Physics Building, Room 204
Note special time.

## "Beyond the Large-Scale Cluster-State Entanglement in the Quantum Optical Frequency Comb – the feasible way from 60 accessible qumodes to thousands"

Chun-Hung Chang , University of Virginia
[Host: Olivier Pfister]
ABSTRACT:

In this talk, I will first give a short introduction about classical computers and quantum computers. I will also introduce cluster states, which are served as the calculating bases of one-way quantum computing. On top of that, I will talk about how we build the cluster states in our lab. Previously, our lab measured 60 qumodes which are simultaneously accessible, but we believe we should have far more than 60. I will explain why we thought we should have thousands accessible qumodes, what hinders us to get more than 60 qumodes, and a feasible way to overcome the difficulties.

Atomic
Monday, April 22, 2019
3:30 PM
Physics Building, Room 204
Note special time.

## "Decoherence in quantum systems: Measurement and control"

Chengxing He , University of Virginia - Physics
[Host: Bob Jones]
ABSTRACT:

Quantum systems are fragile. Inhomogeneities in a sample’s environment can destroy its macroscopic coherence properties, while the coupling of components of a system to unmeasured/uncontrolled environmental degrees of freedom leads to microscopic decoherence. In this talk, I will discuss examples of my work related to macroscopic and microscopic coherence in cold atom ensembles, as well as possible approaches to preserving coherence. In addition, I will discuss a study of topological effects in atomic systems.

Atomic
Monday, April 15, 2019
3:30 PM
Physics Building, Room 204
Note special time.

## "Advances in Polarized Nuclear Imaging"

David Keder , University of Virginia - Physics
[Host: Gordon Cates]
ABSTRACT:

Polarized Nuclear Imaging (PNI) is a novel modality in which images of certain radioactive tracers are formed using conventional Magnetic Resonance Imaging (MRI) techniques by detecting asymmetries in gamma ray emission rates with respect to the nuclear magnetic moments of the tracer.  This modality combines the spatial resolution and contrast provided by MRI with the detection sensitivity of nuclear imaging, allowing for the production of an image using many orders of magnitude fewer nuclei than would be necessary with conventional MRI.  However, many challenges remain in bringing PNI from the laboratory to practice in a clinical setting.  For example, the first PNI image produced took 60 hours to acquire.  In my talk I will describe some novel techniques in currently in development intended to bridge the gap between laboratory and clinic.

Atomic
Monday, April 1, 2019
3:30 PM
Physics Building, Room 204
Note special time.

## "Measuring Core Polarizability of Rubidium-87 using RF Spectroscopy of Rydberg States"

Seth Berl , University of Virginia - Physics
[Host: Cass Sackett]
ABSTRACT:

The core electrons make a significant contribution to the total electric polarizability a of many-electron atoms like Rb. If the core contribution can be determined accurately, the remaining valence contribution to a provides constraints on the wave function and matrix elements of the valence electron. This can be useful for interpreting experiments such as parity violation or radiation shifts in atomic clocks. We report here on a measurement of the core polarizability based on radio-frequency spectroscopy of Rydberg states with large angular momentum. Preliminary results are 9.07 ± 0.01 a.u. for the dipole polarizability ad and 18.3 ± 0.5 a.u. for the quadrupole polarizability aq. These preliminary results are consistent with previous measurements, and uncertainties are reduced by approximately a factor of 4. The dipole polarizability is consistent with high-precision theoretical calculations, but a large discrepancy between theory and experiment persists for the quadrupole value.

Atomic
Monday, March 4, 2019
3:30 PM
Physics Building, Room 204
Note special time.

## "Spin Transport in Fermi Gases Across the Superfluid Transition"

Ariel Sommer , Lehigh University
[Host: Peter Schauss]
ABSTRACT:

Transport properties provide an important tool to characterize many-body systems. In particular, measurements of spin transport in strongly interacting Fermi gases can help to resolve the debate regarding the existence of a pseudogap--a pairing gap above the superfluid critical temperature--in the unitary Fermi gas. Studies of universal bounds on transport coefficients further motivate interest in spin transport in the unitary Fermi gas, which is expected to exhibit timescales approaching the "Planckian" limit set by the temperature, Boltzmann constant, and Planck's constant. I will describe proposed experiments to measure the spin transport coefficients in Fermi gases at low temperatures that can address these questions. Our experimental approach utilizes a homogeneous Fermi gas separated into three regions: a sample and two reservoirs. Non-equilibrium initial conditions in the reservoirs will drive a spin current through the sample, enabling measurements of the spin diffusivity. Our experimental approach can be extended to measurements of heat transport and non-equilibrium states.

Atomic
Monday, February 18, 2019
3:30 PM
Physics Building, Room 204
Note special time.

## "A large-area Sagnac interferometer using atoms in a time-orbiting potential"

Eddie Moan , University of Virginia - Physics
[Host: Cass Sackett]
ABSTRACT:

We describe the implementation of a dual Sagnac interferometer using a Bose-Einstein condensate confined in a harmonic time-orbiting potential magnetic trap, which is sensitive to rotations on the order of Earth’s rate.  Atoms are manipulated using Bragg laser beams to produce two reciprocal interferometers, providing common-mode rejection of accelerations, trap fluctuations, and other noise sources. The Sagnac rotation phase is differential between the two interferometers. The orbit of the atoms is nearly circular, with an effective Sagnac area of about 0.5 mm^2.  This technique has potential applications in terrestrial and space-based inertial navigation systems, which currently use more unstable and less rotation-sensitive optical gyroscopes.

Atomic
Monday, January 28, 2019
3:30 PM
Physics Building, Room 204
Note special time.

## "Rare-earth atoms in solids as a platform for quantum networks "

Elizabeth Goldschmidt , US Army Research Laboratory
[Host: Peter Schauss]
ABSTRACT:

I will give an overview of the emerging field of rare-earth atoms in solids as the basis for a variety of quantum information applications. These systems have a number of advantageous properties including long inherent coherence times, lack of motional dephasing or substantial spectral diffusion, and high density, that make them promising systems for important quantum information tasks, such as long-lived, efficient photonic quantum memory. A major challenge associated with most atom-like quantum emitters in solids, rare-earth atoms included, is the inhomogeneous broadening of the optical transition energy caused by site-to-site variation in the local environment. I will discuss initial experimental results on the effect of this broadening on electromagnetically induced transparency in a europium doped sample. Finally I will present our plans and ongoing work to mitigate the effects of inhomogeneity by investigating a new class of materials.

Atomic
Monday, January 21, 2019
3:30 PM
Physics Building, Room 204
Note special time.

## "Ultrafast intense laser interaction with molecules and nanostructures"

Ali Azarm , University of Arizona
[Host: Bob Jones]
ABSTRACT:

Strong laser field interaction with materials is rich in physics and chemistry, and gives rise to variety of spectacular phenomena ranging from multiphoton/tunneling ionization to high harmonics generation. In this talk, I will present three of these intriguing phenomena that I have investigated.

First, I will explain neutral dissociation of hydrogen molecule in strong laser field through multiphoton super-excitation. I will demonstrate the experimental results of fragmentation of hydrogen molecules in a strong laser field including observation of Balmer lines from hydrogen atoms and measuring the upper limit of the lifetime of the super-excited states by an ultrafast pump and probe experiment [1].

The second part of the talk is dedicated to optical gain and population inversion in ions at 428 nm wavelength through high-resolution spectroscopy. I will clarify how sufficient dissimilarity of rotational distributions in the upper and lower emission levels could lead to gain without net electronic or vibronic population inversion [2].

Finally, at the third part of the talk, I will show the results of use of femtosecond laser pulses to melt indium semi-spherical nanostructure (r~175 nm) and shape them by high spatial frequency laser induced periodic surface structures into linear microstructures of 2 μm long in the direction of laser polarization. The understanding of the modification process, melting and moving in the nano-grating structured field, pave the way to design nanostructures of arbitrary shapes at the sub-wavelength scale [3].

[1] A. Azarm, D. Song, K. Liu et al. J. Phys. B: At. Mol. Opt. Phys. 44 (2011) 085601

[2] A. Azarm, P. Corkum, P. Polynkin, Phys. Rev. A Rapid Comm. 96 (2017) 051401(R)

[3] A. Azarm, F. Akhoundi, R. A. Norwood et al. Appl. Phys. Lett. 113 (2018) 033103

Atomic
Monday, January 7, 2019
3:30 PM
Physics Building, Room 204
Note special time.

## "Conditions for optical parametric oscillation with a structured light pump"

Dr. Gabriel Bie Alves , Universidade Federal Fluminense, Brazil
[Host: Olivier Pfister]
ABSTRACT:

We investigate the transverse mode structure of the down-converted beams generated by a type-II optical parametric oscillator (OPO) driven by a structured pump. Our analysis focus on the selection rules imposed by the spatial overlap between the transverse modes of the three fields involved in the non-linear interaction. These rules imply a hierarchy of oscillation thresholds that determine the possible transverse modes generated by the OPO, as remarkably confirmed with experimental results.

Atomic
Monday, November 26, 2018
3:30 PM
Physics Building, Room 313
Note special time.
Note special room.

## "Precision Measurement and Quantum Chemistry with Ultracold 88Sr2 Molecules"

Stanimir Kondov , Colombia University
[Host: Peter Schauss]
ABSTRACT:

At Tanya Zelevinsky’s lab at Columbia, our current effort focuses on characterizing the strontium molecule with the goal to develop an ultra-precise molecular clock---similar to better-known atomic optical clocks---with unique sensitivity to the fundamental constants of nature such as the gravitational constant G and the electron-to-proton mass ratio. Through precision measurements, one may investigate fundamental problems that are otherwise studied in high-energy (accelerator) research and astrophysical observations.

The implementation of a molecular clock relies on detailed knowledge of the Sr2 molecule. Studies of photodissociation, combined with spectroscopic data, have helped develop a state-of-the-art quantum chemistry model. The predictive value of the model is tested against experimental photodissociation data with remarkable complexity. The model faithfully reproduces the photofragment distributions and helps illuminate a quantum-to-classical crossover in dissociation dynamics.

We have demonstrated the operation of a molecular clock by coherently transferring molecules from a shallow bound state to near the bottom of the molecular potential. Using a magic wavelength technique, we have improved transition quality by 3.5 orders of magnitude, projecting a clock accuracy better than 10-14.

Atomic
Monday, October 29, 2018
3:30 PM
Physics Building, Room 313
Note special time.
Note special room.

## "Spin-specific AC Zeeman potentials"

Seth Aubin , William & Mary
[Host: Cass Sackett]
ABSTRACT:

Spin-specific trapping and mechanical control of ultracold atoms is difficult with current techniques, but offers the possibility of exploring new physics systems, notably spin-dependent trapped atom interferometers, as well as quantum gates, 1D many-body spin gases, and novel cooling schemes. Microwave near-field potentials based on the AC Zeeman effect provide a mechanism for such spin-specific control of atoms: in principle, independent potentials can be targeted to different spin states simultaneously. We present recent experimental progress in implementing such control by using AC near-fields on an atom chip to drive hyperfine transitions and manipulate ultracold rubidium atoms.

Atomic
Friday, May 25, 2018
3:30 PM
Physics Building, Room 313
Note special date.
Note special time.
Note special room.

## "Spectroscopy of sympathetically cooled CaH+ in Coulomb crystals"

Aaron Calvin , Georgia Tech
[Host: Bob Jones]
ABSTRACT:

CaH+ is an astrophysically relevant molecule with proposed applications in fundamental physics. We use CaH+ co-trapped with Doppler cooled Ca+ to perform spectroscopy using two-photon photodissociation with a frequency doubled, mode locked Ti:sapph laser. This method was used to measure the vibronic spectrum of the 11 Σ, v = 0  21 Σ, v' = 0, 1, 2, 3 transitions. Spectroscopy on the deuterated isotopologue, CaD+ confirmed a revised assignment of the CaH+ vibronic levels and a disagreement with MS-CASPT2 theoretical calculations by approximately 700 cm-1. Updated high-level coupled-cluster calculations that include core-valence correlations reduce the disagreement between theory and experiment to 300 cm-1.  The broad bandwidth of the pulsed Ti:sapph provided an advantage for the initial search for transitions, but did not allow spectral resolution of rotational transitions. Pulse shaping was applied to spectrally narrow the linewidth of the pulsed laser to obtain rotational constants for the 21 Σ, v' = 0, 1, 2, 3 and 11 Σ, v = 0 states. This measurement has value in the control of quantum states of the molecule for high precision measurements of rovibrational transitions using quantum logic. Molecule-cold atom collisions for possible buffer gas cooling can also be tested using this method.

Atomic
Monday, May 14, 2018
11:00 AM
Physics Building, Room 313
Note special time.
Note special room.

## "Quantum state preparation and characterization using photon-number-resolving measurements"

Rajveer Nehra , UVA-Department of Physics
[Host: Olivier Pfister]
ABSTRACT:

Quantum state preparation and characterization are essential to emerging near-term quantum technological applications. In particular, single-photon Fock states are of interest as their exciting applications in linear optical quantum computing, quantum internet, quantum communication, quantum sensing, and quantum imaging.

In this work we prepare a single-photon Fock state by heralding two-mode spontaneous parametric down conversion in a PPKTP based optical parametric oscillator (OPO). We then reconstruct the Wigner quasi-probability distribution by Photon-Number-Resolving (PNR) based quantum state tomography. This method circumvents the need for numerical tomographic reconstruction of the state by inverse Radon transform with the balanced homodyne detection method. We perform PNR measurements using transition edge sensor which can resolve up to five photons at 1064 nm. Here we report our recent results of reconstructed negative Wigner function with a final detection efficiency of 56 %.

Towards the end of my talk, I will discuss a method known as Fock state filtering to generate non-classical states using single-photon states, linear optics and PNR resolving measurements.

Atomic
Wednesday, April 4, 2018
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

## "A trapped-atom enclosed-area interferometer using reciprocal circular trajectories"

Edward Moan , UVA-Department of Physics
[Host: Cass Sackett]
ABSTRACT:

We describe progress towards a rotation sensor using ultracold atoms.  A Bose-Einstein condensate is loaded into weak cylindrically symmetric harmonic trap.  The condensate is split and recombined using off-resonant Bragg laser pulses.  After the clouds are split, they oscillate in the trap.  By analyzing the trajectories of the clouds we can optimize the trap such that the frequency is equal along different axes.  Next, we split the condensate twice, creating four clouds that traverse a circular path around the trap center.  After completing an integer number of orbits the clouds can be recombined, forming two reciprocal interferometers whose phase difference is sensitive to rotations but rejects other common-mode noise sources.  We have observed closed circular trajectories with a diameter of 0.6 mm, corresponding to a Sagnac phase of 1500 seconds times the rotation rate, or about 0.1 rad for an Earth-rate rotation.

Atomic
Monday, April 2, 2018
3:30 PM
Physics Building, Room 204
Note special time.

## "THz enhanced Surface Second Harmonic Generation"

Sanjay Khatri , UVA-Department of Physics
[Host: Bob Jones]
ABSTRACT:

When a material is exposed to an intense laser field, the absence of inversion symmetry at the surface can result in the formation  of a non-linear surface polarization and surface second harmonic (SSH) emission. We find that the SSH yield from a metal can be dramatically influenced by the presence of an additional THz field. In the experiments, collinear 100fs 780nm laser and 2ps single-cycle THz beams are focused at grazing incidence along a gold surface. The SSH yield is measured as a function of the THz intensity, relative laser-THz delay, and laser/THz polarizations relative to the surface normal. The yield from an optically flat gold mirror increases by as much as a factor of three in the presence of a 20kV/cm THz eld. Interestingly, the SSH enhancement for the same THz field is as large as a factor of 27 if the gold mirror is replaced by a gold-coated diffraction grating, apparently due to either a local THz field enhancement or increased sensitivity of the non-linear polarization to the THz field near grating micro-structures. We are exploring the use of THz-enhanced SSH emission to characterize the THz-field enhancement and/or response of micro-structured metal surfaces with other geometries.

Atomic
Monday, February 26, 2018
3:30 PM
Physics Building, Room 204
Note special time.

## "Clocks and interferometers with cold atoms"

Erling Riis , University of Strathclyde
[Host: Cass Sackett]
ABSTRACT:

The use of cold atoms has led to a substantial increase in the accuracy achievable in many atomic physics measurements. This has most notably been demonstrated in the atomic clock relying on the interference of internal states of weakly interacting atoms in free fall. However, it has also led to an additional layer of experimental complexity which, combined with the physical size of state-of-the-art setups, impose significant limitations on wider practical applications. Progress will be reported on the development of a compact atomic clock based on cold atoms.

Unprecedented precision has also been demonstrated in atom interferometers relying on the  detection of differential phase shifts between atomic wavefunctions of e.g. different motional states. Sensitivity to external interactions results in a shift of the atomic phase relative to a lab-frame reference, typically the spatial phase of an optical standing wave. This is a limitation to practical measurements as it requires long temporal stability and has motivated the investigation of an atom interferomenter inherently insensitive to the phase noise of the readout system. This relies on an atomic homodyne detection allowing the entire interferometric signal to be read out in a single shot.

Atomic
Monday, January 29, 2018
3:30 PM
Physics Building, Room 204
Note special time.

## "Leveraging qumode scalability: increased squeezing and entanglement from redistributed multitudinous-mode squeezing"

Zack Carson , UVA - Department of Physics
[Host: Olivier Pfister]
ABSTRACT:

Quantum computing harnesses purely non-classical features of quantum physics to perform computations that would be otherwise infeasible on a traditional (classical) computer. Highly squeezed states are a crucial resource for many quantum technologies, primarily fault tolerant quantum computing. As with any quantum resource, squeezing is very fragile and arduous to generate experimentally. Because of this, the 20.5 dB squeezing level germane to the fault tolerance threshold (for an error rate of 0.00001) of continuous variable (CV) quantum computing has yet to be obtained, despite recent progress. I propose an experimental method designed to breach this threshold by unitarily redistributing multitudinous-mode squeezing into a highly squeezed single qumode (the CV analog of a qubit, or quantum bit). This new paradigm utilizes multi-mode states as a squeezing resource, by effectively transferring small levels of squeezing per qumode over N modes into a single qumode with N-times the squeezing.

Atomic
Monday, October 16, 2017
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "What is the temperature of an ultra-cold Rydberg plasma?"

Duncan Tate , Colby College
[Host: Tom Gallagher]
ABSTRACT:

In this talk, I'll report on a systematic experimental and numerical study of the electron temperature in ultra-cold plasmas which evolve from samples of cold Rydberg atoms. Specifically, we have measured the asymptotic expansion velocities of ultra-cold plasmas (UNPs) which evolve from cold, dense, samples of Rydberg rubidium atoms using ion time-of-flight spectroscopy. From this, we have obtained values for the initial plasma electron temperature, as a function of the original Rydberg atom density and binding energy. We have also simulated numerically the interaction of UNPs with a large reservoir of Rydberg atoms to obtain data to compare with our experimental results. We find that, for n > 40, the electron temperature in the Rydberg plasma is insensitive of the initial ionization mechanism which seeds the plasma. Instead, it is determined principally by the plasma environment when the UNP decouples from the Rydberg atoms at the end of the avalanche regime, and this occurs when the plasma electrons are too cold to ionize the remaining Rydberg population. On the other hand, plasmas from Rydberg samples with n < 40 evolve in a different manner. There is very little additional ionization after the plasma reaches threshold as the electrons in the plasma have insufficient energy to ionize the parent atoms. Consequently, the only significant interaction between the plasma and the parent atoms causes the Rydberg atoms to be de-excited, and the electron temperature equilibrates at a fraction of the initial Rydberg atom binding energy.

SLIDESHOW:
Atomic
Monday, September 25, 2017
3:30 PM
Physics Building, Room 204
Note special time.

## "Fock state responsivity of single photon detectors"

Zubin Jacob , Purdue University
[Host: Olivier Pfister]
ABSTRACT:

Highly efficient single photon detectors are ubiquitous in quantum optics and atomic physics. However, many of the theories of single photon detection still arise from the Glauber theory of photodetection which was primarily developed for inefficient detectors (weak light-matter coupling). The first goal of the talk is to contrast the photon counting mechanism in photomultiplier tubes (PMTs), single photon avalanche diodes (SPADs), single electron transistor based photodetectors (SET-PDs) and superconducting nanowire single photon detectors (SNSPDs). This can help develop a general model for single photon detection beyond Glauber's theory.

Secondly, we will present experimental results on time-correlated single photon counting experiments that demonstrate long range dipole-dipole interactions between quantum emitters mediated by metamaterials.   We will discuss a fundamental limit to the efficiency of energy transfer between quantum emitters and discuss routes to achieve this limit through induced coherence. Our approach to engineering dipole-dipole interactions can motivate experiments from atomic systems (eg: Rydberg blockade) to biochemistry (Forster/Dexter resonance energy transfer).

Nuclear

Monday, April 17, 2017
3:30 PM
Physics Building, Room 204
Note special time.

## "Target and Polarimetry studies for GEn and An1 experiments at JLab"

Sumudu Katugampola , UVA- Department of Physics
[Host: Gordon Cates]
ABSTRACT:

An upcoming measurement at Jefferson Laboratory (JLab) of the electric form factor of the neutron (GEn) will utilize a polarized 3He target at high luminosity. While polarized 3He targets at JLab have previously been made entirely of glass, we describe progress toward six liter, convection style target cells incorporating metal windows for the electron beam. We have found good performance by using Oxygen Free High Conductivity (OFHC) copper substrates electroplated with gold. We have further established that Uranium glass (Canary glass) has excellent spin-relaxation properties, and can serve as a transition glass from Pyrex to Aluminosilicate glass (GE180). We also present polarimetry results of our first production, “Stage 1”, all-glass target cell that is to be used in the measurement of the virtual photon spin asymmetry of the neutron (A1n) at JLab. Further, we present preliminary results of a custom built, low noise NMR system which will be used in the precision measurement of the atomic parameter k0, which is important for the accurate understanding of the 3He polarization and which characterizes the 3He-Rb system.

Atomic
Monday, February 27, 2017
11:00 AM
Physics Building, Room 313
Note special time.
Note special room.

## "Quantum computing and topological codes using continuous variables"

Nicolas Menicucci , RMIT University, Melbourne, Australia
[Host: Olivier Pfister]
ABSTRACT:

Continuous-variable (CV) approaches to quantum computing have certain advantages over standard qubit-based approaches. The most striking of these is the ability to make extremely large resource states for measurement-based quantum computing using small optical setups. Furthermore, local measurements on one of these states will transform it into a CV version of a topological quantum code, which has potential applications in condensed-matter theory, anonymous broadcasting, and quantum error correction. My talk will discuss the latest theoretical and experimental developments in this research area.

Atomic
Monday, November 7, 2016
3:30 PM
Physics Building, Room 204
Note special time.

## "Quantum Metrology (1/4)"

Luiz Davidovich (recorded lecture at CollÃ¨ge de France)
[Host: Olivier Pfister]
Special Lecture in Biophysics

Monday, October 17, 2016
4:00 PM
Jordan Hall, Room Conference Center
Note special room.

## "CryoEM of Molecular Machines at Atomic Resolution"

Wah Chiu , Baylor College of Medicine
ABSTRACT:

The ability of electron cryo-microscopy (cryoEM) to rapidly and routinely determine the atomic structures for biological complexes has transformed the interface of chemistry and biology. Previously, determining structures at this resolution was only ossible by X-ray crystallography and NMR spectroscopy, which could be slow, difficult, and for many complexes impossible.

Over the last few years the EM database shows a dramatic increase in the number of cryoEM maps at a resolution higher than 4 Å:

Year   # 3D maps
2012        4
2013        7
2014       36
2015     114
2016     167 (as of Oct. 7th)

Dr. Chiu has been a major contributor to this "resolution revolution,” and his presentation is entitled "CryoEM of Molecular Machines at Atomic Resolution.”

Dr. Chiu received his BA in Physics (1969) and PhD in Biophysics (1975) from the University of California, Berkeley. He is the Alvin Romansky Professor of Biochemistry and the Distinguished Service Professor at Baylor College of Medicine in Houston, Texas. He is a pioneer in methodology development for electron cryo-microscopy. His work has made multiple transformational contributions in developing single particle electron cryo-microscopy as a tool for the structural determination of molecular machines towards atomic resolution.

For three decades, Dr. Chiu has directed an NIH funded 3DEM Resource Center. He has solved many cryoEM structures including viruses, chaperonins, membrane channels, cytoskeleton protein complexes, protein-DNA complexes and RNA complexes in collaboration with many scientists around the world. His 3DEM Resource Center continues to establish high standard testing and characterization protocols for cryoEM instrumentation and to develop new image processing and modeling algorithms for cryoEM structure determination.

Dr. Chiu is the co-founder of the W.M. Keck Center for Computational Biology and the graduate program in Structural and Computational Biology and Molecular Biophysics in the early 1990s. These cross-disciplinary and cross-institutional programs involve hundreds of faculty from 7 academic institutions in the Greater Houston Area and have trained many eminent scientists fluent in quantitative biomedicine.

Dr. Chiu’s research, collaboration and training efforts have been recognized by his elected membership to the Academia Sinica, Taiwan (2008) and the United States National Academy of Sciences (2012).  Other honors include the Distinguished Science Award from the Microscopy Society of America (2014) and an Honorary Doctorate of Philosophy from the University of Helsinki, Finland (2014).

Dr. Chiu's visit is sponsored and hosted by the
- UVa Program in Biophysics (Dr. Robert Nakamoto)
- Department of Molecular Physiology and Biological Physics (Drs. Wladek Minor, Zygmunt Derewenda and Mark Yeager)
-Department of Biochemistry and Molecular Genetics (Drs. Ed Egelman and Anindya Dutta).

Atomic
Monday, September 26, 2016
3:30 PM
Physics Building, Room 204
Note special time.

## "A Compact, All-optical Rubidium Clock with H-MASER Stability"

John Burke , Air Force Research Lab
[Host: Cass Sackett]
ABSTRACT:

This seminar will present an optical atomic clock based on a two-photon transition at 778 nm in rubidium that could be made small and robust enough to be used outside of a laboratory environment. We will cover the clocks principals of operation, fundamental limitations and data supported current status. We will show that this system is fundamentally capable of besting a hydrogen MASER in frequency stability and size.

Atomic
Monday, September 19, 2016
11:00 AM
Physics Building, Room 313
Note special time.
Note special room.

## "Electrons playing tag upon photoionization of atoms"

Yoshiro Azuma , Sophia University, Tokyo
[Host: T. Gallagher]
ABSTRACT:

Two cases of strong manifestation of electron correlation upon innervalence photoionization of rare gas atoms with syncrhtron radiation will be discussed.
1. Photoelectron recapture due to post-collision interactions between Auger electrons and photo electrons.  In our new high resolution Auger electron spectroscopy results, the Rydberg series structure of ionic final states appear in the structure of the Auger peak.  Rich structure due to angular momentum states were resolved and angular distribution information was obtained for the first time.
2. We demonstrated that fluorescence lifetime measurements upon innervalence excitation can be very sensitive to electron correlation and provide information regarding configuration interaction that cannot otherwise be obtained

Atomic
Monday, September 19, 2016
3:30 PM
Physics Building, Room 204
Note special time.

## "Modeling Strong-Field Ionization in Molecules using Range-Separated Time-Dependent Density Functional Theory"

Ken Lopata , Louisiana State University
[Host: Bob Jones]
ABSTRACT:

Strong-field ionization (SFI) and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses validity basis sets, and the intense fields which require non-perturbative electronic structure methods. In this talk I present recent developments towards extending time-dependent density functional theory (TDDFT) for SFI using atom-centered basis sets and tuned range-separated hybrid DFT functionals. Unlike traditional TDDFT, this approach has the correct long-range Coulomb potential and reduced self-interaction errors.  The resulting laser intensity, angle, and molecular orbital-dependent ionization rates for N2 and iodoacetylene show good agreement with experimental values. This method opens the door to predictive simulations of ionization and ionization-triggered dynamics in large molecular systems without inputs from experiment. For more details see: Sissay et al, J. Chem. Phys. 145, 094105 (2016).

Atomic
Monday, June 6, 2016
4:00 PM
Physics Building, Room 204

## "Arrested relaxation in an isolated molecular ultracold plasma"

Edward Grant , University of British Columbia
[Host: T. Gallagher]
ABSTRACT:

While small isolated quantum systems undergo well-defined wave packet dynamics, the observables in very large, locally isolated quantum systems generally relax to states of maximum entropy. To explain this, the eigenstate thermalization hypothesis (ETH) holds that the unitary dynamics of arbitrary superpositions yield equilibrium expectation values as a time-average [1, 2]. Thus, in this picture – despite the deterministic nature of the Schro¨dinger equation and the absence of outside perturbations – an arbitrarily prepared isolated quantum system relaxes to a thermal equilibrium that is somehow hardwired in its eigenstates. Indeed, unimolecular rate theory depends on energy randomization, and quantum systems as small as three transmon qubits exhibit ergodic dynamics. [3].

But, theory predicts the existence of certain interacting many-body systems that lack intrinsic decoherence and preserve topological order in highly excited states. These systems exhibit local observables that retain a memory of initial conditions for arbitrarily long times. Such behaviour has important practical and fundamental implications. For this reason, experimental realizations of isolated quantum systems that fail to thermalize have attracted a great deal of interest [4, 5].

Here we describe particular conditions under which an ultracold plasma evolves from a molecular Rydberg gas of nitric oxide, adiabatically sequesters energy in a reservoir of mass transport, and relaxes to form a spatially correlated strongly coupled plasma. Short-time electron spectroscopy provides evidence for complete ionization. The long lifetime of the system, particularly its stability with respect to recombination and neutral dissociation, suggest a robust process of self-organization to reach a state of arrested relaxation, far from thermal equilibrium.

[1] Rigol M, Dunjko V, Olshanii M: Thermalization and its mechanism for generic isolated quantum systems. Nature

2008,  452(7189):854–858.

[2] Eisert J, Friesdorf M, Gogolin C: Quantum many-body systems out of equilibrium. Nature Physics 2015, 11(2):124– 130.

[3] Neill C, et al: Ergodic dynamics and thermalization in an isolated quantum system. arXiv: 2016, 1601.00600v2. [4] Kondov SS, McGehee WR, Xu W, DeMarco B: Disorder-Induced Localization in a Strongly Correlated Atomic

Hubbard Gas. Phys Rev Lett 2015, 114(8):083002.

[5] Schreiber M, Hodgman SS, Bordia P, Lu¨schen HP, Fischer MH, Vosk R, Altman E, Schneider U, Bloch I: Observation of many-body localization of interacting fermions in a quasi-random optical lattice. Science 2015, 349:842–845.

Atomic
Tuesday, May 31, 2016
3:30 PM
Physics Building, Room 203
Note special date.
Note special time.
Note special room.

## "Test of Lorentz symmetry with trapped ions"

Thaned Pruttivarasin
[Host: T. Gallagher]
ABSTRACT:

The outcome of an experiment should not depend on the orientation of the apparatus in space. This important cornerstone of physics is deeply engrained into the Standard Model of Physics by requiring that all fields must be Lorentz invariant. However, it is well-known that the Standard Model is incomplete. Some theories conjecture that at the Planck scale Lorentz symmetry might be broken and measurable at experimentally accessible energy scales. Therefore, a search for violation of Lorentz symmetry directly probes physics beyond the Standard model. We present a novel experiment utilizing trapped calcium ions as a direct probe of Lorentz-violation in the electron-photon sector. We monitor the energy between atomic states with different orientations of the electronic wave-functions as they rotate together with the motion of the Earth. This is analogous to the famous Michelson-Morley experiment. To remove magnetic field noise, we perform the experiment with the ions prepared in the decoherence-free states. Our result improves on the most stringent bounds on Lorentz symmetry for electrons by 100 times. The experimental scheme is readily applicable to many ion species, hence opening up paths toward much improved test of Lorentz symmetry in the future.

Condensed Matter Seminar

Monday, April 25, 2016
3:45 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Symmetric surfaces of three dimensional topological superconductor"

Sharmistha Sahoo , UVA-Department of Physics
ABSTRACT:

Symmetry-protected topological phases have gapless surface (edge) states. These states are robust against any single-body perturbation that has the symmetry, as long as the gap in the bulk spectrum is not closed. Recently, it is found that these gapless surface states can be gapped when many-body interaction is included. In this talk, I will discuss what kind of many-body interaction opens a gap in the surface of topological superconductor without breaking its symmetry.

Time reversal symmetric topological superconductor carries gapless Majorana fermion on the surface. I will discuss the “Coupled Wire Model” which we built to mimic the massless Majoranas in the surface. I will talk about how the explicit many-body inter-wire interaction, that we introduced, preserves time reversal symmetry but opens a gap in the surface spectrum. I will also discuss the resulting gapped surface carrying non-trivial topological order evident from the anyon structure that we find.

SLIDESHOW:
Special Quantum Optics and Quantum Information Seminar

Thursday, April 21, 2016
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

## "Entanglement of light in crystals and photonic chips. "

Paulo Nussenzveig , Universidade São Paulo, Brazil
[Host: Olivier Pfister]
ABSTRACT:

Entanglement of bright beams of light is a useful resource for applications in information protocols. By using continuous variables, much in the spirit of the original analysis by Einstein, Podolsky, and Rosen, it is possible to perform deterministic tasks and also to use detection tools available to classical communications systems.  We have concentrated our efforts on nonlinear optical processes using bulk crystals inside optical cavities.  The cavity bandwidth sets a maximum repetition rate for information processing and communications.  An interesting pathway consists in investigating similar effects in miniaturized cavities on photonic chips, with the additional benefit of compatibility with micro-electronics.  In this talk, I will present an overview of our research on the generation of continuous-variable entanglement in bulk nonlinear crystals, as well as nonclassical light generated in silicon chips.

Atomic
Monday, April 11, 2016
3:30 PM
Physics Building, Room 204
Note special time.

## "Dipole – Dipole Induced Transitions in Rydberg Atom Pairs "

Kapila Wijayaratne , UVA- Physics Department
ABSTRACT:

Rydberg Atoms have pronounced dipole moments and dipole – dipole interactions lead to the pairing up of Rydberg atoms to form transient diatomic Rydberg molecules under special conditions. Resonant microwave transitions from pairs of Rb atoms have been observed and a configuration interaction model can be used to understand this phenomena.

Condensed Matter Seminar

Monday, April 4, 2016
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Exchange Bias and Bi-stable Magneto-Resistance States in Single-Layer Amorphous TbFeCo and TbSmFeCo Thin Films"

Chung Ting (Marco) Ma , UVA- Department of Physics
ABSTRACT:

Amorphous ferrimagnetic TbFeCo and TbSmFeCo thin films are found to exhibit exchange bias and bi-stable magneto-resistance states near compensation temperature. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive spectroscopy mapping reveal two nanoscale amorphous phases with different Tb concentrations distributed within the amorphous films. The observed exchange anisotropy originates from the exchange interaction between the two nanoscale amorphous phases. The micromagnetic model is adopted to study this heterogeneous magnetic material with two interpenetrating nanoscale phases. This study can serve as a platform for developing exchange bias materials with ferrimagnet.

SLIDESHOW:
Special Quantum Information/Mathematical Physics Seminar

Tuesday, March 29, 2016
3:30 PM
Physics Building, Room 313
Note special date.
Note special time.
Note special room.

## "Non-demolition measurements and their perturbations"

Matt Fraas , Ludwig-Maximilians-Universität Munich
[Host: Israel Klich ]
ABSTRACT:

Indirect measurements, of which non-demolition measurements is a specific subclass, describe a physical situation in which an information about a quantum system is acquired through a direct measurement on a sequence of probes subsequently interacting with the system. Recent interest in the field originates in the photon counting experiments of Haroche. Mathematically the problem is equivalent to the study of statistics of long products of completely positive maps. I describe this mathematical theory with a special focus on the non-demolition subclass -- this is the case when all the map commutes -- and its small perturbation.

Atomic
Monday, March 28, 2016
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "High-precision measurements of the Rb87 D-line tune-out wavelength"

Adam Fallon , UVA- Physics Department
[Host: Olivier Pfister]
ABSTRACT:

I will report a measurement of a light wavelength at which the ac electric polarizability equals zero for Rb87 atoms in the F=2 ground hyperfine state. The experiment uses a condensate interferometer to find this “tune-out” wavelength for the scalar polarizability, which lies at 790.032388(32) nm. This result can be used to determine the ratio of matrix elements R = 1.99221(3), a 100-fold improvement over previous experimental values. I will discuss techniques for accurate determination and control of light polarization as well as progress on measurements of the vector polarizability between the D1 and D2 spectral lines. Measurements of tune-out wavelengths and the vector polarizability between multiple lines allows separation of individual contributions to the polarizability from higher-lying states and the core up to ratios of matrix elements. Accurate knowledge of these ratios should serve useful as a theoretical benchmark and in atomic parity violation experiments.

SLIDESHOW:
Atomic
Tuesday, March 1, 2016
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

Slideshow (PDF)

## ""Catalysis of Stark-tuned Interactions between Ultracold Rydberg Atoms"

Aye Win , Old Dominion University
[Host: Olivier Pfister]
ABSTRACT:

The strong long-range interaction between ultracold Rydberg atoms gives rise to a number of interesting phenomena that have been studied in recent years including resonant energy transfer collisions, many-body quantum simulations, quantum information processing, and ultracold plasmas. The dipole-dipole interaction between a pair of Rydberg atoms can result in a state-changing interaction if the energy defect for the process is small. The collisional energy transfer process can be tuned into resonance via the Stark effect. Such resonances are known as Förster resonances. In this talk, we will discuss a recent study of the time dependence of resonant energy transfer process and of a catalysis effect in the resonant energy transfer between ultracold 85Rb Rydberg atoms. We have investigated the energy transfer process of 34p + 34p → 34s + 35s, and observed Stark-tuned Förster resonances. When additional Rydberg atoms of 34d state are included in the interaction, an increase in the population of 34s states atoms was observed. Although the 34d state atoms do not directly participate in the resonant energy transfer process that produces 34s state atoms (shown above), they add an additional interaction channel 34p + 34d → 34d + 34p that is resonant for all electric fields and results in a change in the rate in which 34s atoms are produced. We will present our experimental results and compare them with model simulations.

SLIDESHOW:
Special Quantum Information Seminar

Wednesday, January 27, 2016
3:30 PM
Physics Building, Room 313
Note special date.
Note special time.
Note special room.

## "Special Quantum Information Seminar"

Rafael Alexander
[Host: Olivier Pfister]
Atomic
Monday, January 11, 2016
3:30 PM
Physics Building, Room 204
Note special time.

## "Ultrafast Optical Frequency Comb: from laser dynamics to quantum networks"

Prof. Nicolas Treps , Université Pierre et Marie Curie
[Host: Olivier Pfister]
ABSTRACT:

Ultrafast frequency combs have found tremendous utility as precision instruments in domains ranging from frequency metrology, optical clocks, broadband spectroscopy, and absolute distance measurement. This sensitivity originates from the fact that a comb carries a huge number of co-propagating, coherently-locked frequency modes. Accordingly, it is the aggregate noise arising from these individual teeth that limits the achievable sensitivity for a given measurement. Correlations among various frequencies are the key factor in describing and using an optical frequency comb. We have developed methods, inspired from quantum optics, to extract amplitude and phase correlations among a multitude of spectral bands. From these, we can deduce the spectral/temporal eigenmodes of a given optical frequency comb (OFC), and use it to either study the dynamics or the laser, or to optimize metrology experiments such as, for instance, ranging in turbulent medium[1,2].

But beyond characterizing the classical covariance matrix of an OFC, one can, using non-linear effects, manipulate this noise and eventually reduce it even bellow quantum vacuum noise, producing squeezed optical frequency combs. We have demonstrated that by proper control of non-linear crystals, optical cavities and pulse shaping it was possible to embed within an optical frequency comb up to 10 spectral/temporal modes with non-classical noise properties[3]. Furthermore, dividing the spectrum of this comb into 10 frequency bands, entanglement is certified for all of the 115974 possible nontrivial partitions of this 10 mode state. This is the first demonstration of full multipartite entanglement[4] and this source is shown to be a very promising candidate for scalable measurement based quantum computing[5].

References

[1]          R. Schmeissner, J. Roslund, C. Fabre, and N. Treps, 113, 263906 (2014).

[2]          P. Jian, O. Pinel, C. Fabre, B. Lamine, and N. Treps, Opt Express 20, 27133 (2012).

[3]          J. Roslund, R. M. De Araujo, S. Jiang, and C. Fabre, Nature Photonics 8, 109 (2014).

[4]          S. Gerke, J. Sperling, W. Vogel, Y. Cai, J. Roslund, N. Treps, and C. Fabre, 114, 050501 (2015).

[5]          G. Ferrini, J. P. Gazeau, T. Coudreau, C. Fabre, and N. Treps, New J Phys 15, 093015 (2013).

Special Quantum Information Seminar

Monday, November 30, 2015
3:30 PM
Physics Building, Room 204
Note special time.

## "The complexity of estimating local physical quantities"

Sevag Gharibian , Virginia Commonwealth University
[Host: Olivier Pfister]
ABSTRACT:

A central direction of research in condensed matter physics is the determination of properties of local Hamiltonian systems. Unfortunately, computing such properties is often intractable, in that the complex matrices involved are typically of exponential size. Over the last 15 years, a burgeoning area of research at the intersection of condensed matter physics and computational complexity theory, known as Quantum Hamiltonian Complexity, has made significant strides in characterizing the complexity of such computational tasks. In this talk, we begin with a gentle introduction to the field of Quantum Hamiltonian Complexity. We then show that a central and basic task in condensed matter physics, computing the expected value of a local observable against the ground state of a local Hamiltonian, is an intractable task in the worst case (assuming standard complexity theoretic conjectures), even if the observable acts on just a single qubit.

This talk is based on joint work with Xiaodi Wu (U Oregon) and Justin Yirka (VCU).

Atomic
Friday, July 10, 2015
4:00 PM
Physics Building, Room 204
Note special date.

## ""Interaction of clusters with intense, few-cycle, long wavelength fields""

Hyunwook Park , Ohio State University
[Host: Thomas Gallagher]
Atomic
Wednesday, July 8, 2015
4:00 PM
Physics Building, Room 204
Note special date.

## ""Atomic Clocks and the Search for Variation of Fundamental Constants""

Professor Marianna Safronova , University of Delaware
[Host: Thomas Gallagher]
Atomic
Tuesday, July 7, 2015
1:30 PM
Physics Building, Room 205
Note special date.
Note special time.
Note special room.

## "TBA"

Safra Niyaz
[Host: Thomas Gallagher]
Atomic
Monday, April 20, 2015
3:30 PM
Physics Building, Room 204
Note special time.

## "Molecular photoionization in strong fields"

Peter Sandor , Stonybrook University
[Host: Bob Jones]
Atomic
Tuesday, April 14, 2015
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

Slideshow (PDF)

## "Microwave transitions between pair states composed of two Rb Rydberg atoms"

Jeonghun Lee , University of Virginia
[Host: Tom Gallagher]
SLIDESHOW:
Atomic
Monday, April 13, 2015
3:30 PM
Physics Building, Room 204
Note special time.

## "Phase Dependence in Above Threshold Ionization Close to the Ionization Limit"

Eric Magnuson , University of Virginia
[Host: Tom Gallagher]
Atomic
Monday, February 23, 2015
3:30 PM
Physics Building, Room 205
Note special time.
Note special room.

Slideshow (PDF)

## "Exploiting the Entanglement in Classical Optics Systems"

Carlos Eduardo Rodrigues De Souza , Fluminense Federal University
[Host: Olivier Pfister]
ABSTRACT:

The combination of the polarization and spatial photonic degrees of freedom open interesting possibilities in the quantum optics and quantum-information domains. The ability to produce and transform beams carrying orbital angular momentum – the optical vortices - has allowed the development of important techniques with potential applications to quantum information. In this seminar I will present some optical devices to quantum information and I will talk about the topological phase, associated with the double connectedness of the SO [3] representation in terms of maximally entangled states. Under local unitary operations on their polarization and transverse degrees of freedom, the vector vortices can only acquire discrete geometric phase values, 0 or π, associated with closed paths belonging to different homotopy classes on the SO(3) manifold. As the meaning results I will show that the topological phase can be evidenced through interferometric measurements and that a quantitative relationship between the concurrence and the fringes visibility can be derived as well.

[1] C. E. R. Souza, J. A. O. Huguenin and A. Z. Khoury Topological phase structure of vector vortex beams, JOSA-A 31, No. 5 1007 (2014).

[2] C. E. R. Souza, J. A. O. Huguenin, P. Milman and A. Z. Khoury Topological Phase for Spin-Orbit Transformations on a Laser Beam PRL 99, 160401 (2007).

[3] C. E. R. Souza and A. Z. Khoury A Michelson controlled-not gate with a single-lens astigmatic mode converter Optics Express 18, No. 9 9207 (2010).

SLIDESHOW:
Quantum Information Seminar
Monday, June 16, 2014
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Exploiting the bandwidth resource of broadband bi-photons: Efficient detection with a bi-photon interferometer"

Avi Pe'er , Bar Ilan University
[Host: Olivier Pfister]
ABSTRACT:
Broadband time-energy entangled photon pairs (bi-photons) from a narrowband pump are in many ways the 'black sheep of the family' in quantum information. Although they are very easily produced in large quantities and demonstrate extreme nonclassical behavior, broadband bi-photons are rarely used in quantum information, mainly because of the bandwidth limitations in detecting them with standard photo-detectors and homodyne techniques. We demonstrate complete measurement of the bi-photons wave-function (amplitude and phase) with near-unit efficiency, using a quantum interference between the generation amplitudes of bi-photons in two separated nonlinear media. I will describe experiments that employ this method with two different ultra-bright and ultra-broadband sources of bi-photons: one based on spontaneous down conversion (SPDC) in a nonlinear crystal, and the other on spontaneous four-waves mixing (FWM) in a nonlinear fiber. With SPDC we measure the quantum purity and the spectral phase of the bi-photon wave-function from the observed fringe pattern and its visibility. With the FWM source we explore the quantum-to-classical transition as pump intensity is varied, and observe quantum collapses and revivals of the interference contrast that are the signature of bi-photon generation with imaginary gain – a unique quantum regime of FWM.

1. Yaakov Shaked, Roey Pomerantz, Rafi Z. Vered and Avi Pe'er, "Observing the nonclassical nature of ultra-broadband bi-photons at ultrafast speed", New J. Phys. 16, 053012 (2014).

2. Rafi Vered, Yaakov Shaked, Michael Rosenbluh and Avi Pe'er, "The Classical-to-Quantum Transition with Broadband Four-Waves Mixing - Observing Bi-photon Generation with Real or Imaginary Gain", Submitted (2014)

3. Faina Shikerman and Avi Pe’er, "Sum-frequency generation as a detector of high-power two-mode squeezing", Phys. Rev. A. 88, 043808 (2013)

SLIDESHOW:
Atomic Research Seminar & GPSA Talk
Monday, April 21, 2014
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "A compact vapor cell for cold atom applications"

Oat Arpornthip , University of Virginia
[Host: Cass Sackett]
ABSTRACT:
Atom traps promise great improvements on a wide range of technologies: Atom interferometry, gravimetry, magnetometry, navigation. Despite orders of magnitude in improvements promised, atom technology has seen limited commercial adoption due to voluminous instrumentation size. We have designed a new type of trap which reduces the apparatus volume by a factor of ten with satisfactory performance. Our design choices and component research will be discussed. We aim to develop a self-contained Rb vapor cell capable of sustaining a magneto-optical trap at a decent background pressure over a long period of time.
SLIDESHOW:
Atomic
Monday, April 14, 2014
3:30 PM
Physics Building, Room 204
Note special time.

## "Using the Dipole-Dipole Force to Control Minimum Atom Separation"

Brian Richards , University of Virginia
[Host: Bob Jones]
GPSA (Graduate Physics Student Association) talk (Primarily meant for students)
Monday, April 7, 2014
2:00 PM
Physics Building, Room 313
Note special time.
Note special room.

## "Creating highly scalable entangled states for the quantum computer"

Moran Chen , University of Virginia
[Host: GPSA]
ABSTRACT:
The quantum computer, whose information is encoded in "qubits” obeying quantum mechanics laws, will be able to perform some calculations exponentially faster than the classical computer whose information is encoded in "bits”. There are two principal models of quantum computing: the circuit model and the measurement-based model. The measurement-based model is crucially based on the cluster state, a type of highly entangled quantum state that serves as the resource and material for the whole calculation. This talk will discuss an original experimental work for the largest cluster state ever created whose modes (optical versions of qubits) are all available simultaneously. The entanglement proceeds from interfering multiple EPR pairs generated from a nonlinear crystal in an optical parametric oscillator, into a very long dual-rail wire cluster state. These highly scalable cluster states serve as building blocks of the universal quantum computer, and also are important resources for studying quantum mechanics in large systems.
Quantum Information Seminar
Thursday, April 3, 2014
2:00 PM
Physics Building, Room 313
Note special date.
Note special time.
Note special room.

Slideshow (PDF)

## "BosonSampling with Controllable Distinguishability of Photons"

Barry Sanders , University of Calgary
[Host: Olivier Pfister]
ABSTRACT:
The BosonSampling Problem is to sample output photon-coincidence probabilities given vacuum and single-photon inputs to a passive interferometer with more channels than photons. This problem is classically hard to simulate as these probabilities are weighted by computationally hard permanents of sub-matrices of the interferometer transition matrix yet efficient to execute quantumly. Our innovation [1,2] introduces distinguishability between photons by controlling arrival times of otherwise identical photons in order to test the model, assess sampling errors and generalize BosonSampling beyond permanent-weighted to immanant-weighted probabilities.
[1] S.-H. Tan, Y. Y. Gao, H. de Guise and B. C. Sanders, “SU(3) Quantum Interferometry with single-photon input pulses”, Physical Review Letters110 (11): 113603 (5 pp.), 12 March 2013, arXiv.org:1208.5677.
[2] H. de Guise, S.-H. Tan, I. P. Poulin and B. C. Sanders, “”Immanants for three-channel linear optical networks”, arXiv.org:1402.2391.
SLIDESHOW:
GPSA (Graduate Physics Student Association) talk (Primarily meant for students)
Monday, November 11, 2013
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Brout-Englert-Higgs Mechanism and Beyond"

Ajinkya S. Kamat (Ph.D. student) , University of Virginia
[Host: GPSA]
ABSTRACT:
In this talk I will elaborate on what the Brout-Englert-Higgs mechanism is and how it leads to masses of the elementary particles in the Nature. I will also talk about what remains to be done on the theoretical front beyond the standard model of particle physics after the discovery of the Higgs boson at LHC and what our research group is doing in that direction. This will be a semi-technical talk understandable to graduate and undergraduate students.

SLIDESHOW:
GPSA (Graduate Physics Student Association) talk (Primarily meant for students)
Monday, October 28, 2013
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Why is the Brout-Englert-Higgs mechanism needed?"

Ajinkya S. Kamat , University of Virginia
[Host: GPSA]
ABSTRACT:
It is now widely known that the Brout-Englert-Higgs mechanism (popular by the name Higgs mechanism) leads to the masses of the elementary particles in Nature. But the answer to 'why do we need Higgs mechanism to give these masses?' is not well known to many outside the field of particle physics. Hence, in this talk I will try to explain answer to this question in a semi-technical way, which is understandable to graduate students having basic conceptual idea about quantum mechanics.
SLIDESHOW:
Atomic
Monday, October 14, 2013
3:30 PM
Physics Building, Room 204
Note special time.

## "Dynamic holographic beam shaping for cold atom manipulation"

Vincent Carrat , University of Virginia
[Host: Tom Gallagher]
ABSTRACT:
Dynamic holography using a spatial light modulator is a very versatile tool for creating arbitrary optical potentials by spatially shaping a laser beam. These potentials can be used for cold atoms manipulation. In order to produce accurate optical potentials by shaping a laser beam we need high quality holograms. Nevertheless SLMs suffer from defects which limit the quality. To measure defects we have developed a method based on polarimetry to get the birefringence map of the SLM. Birefringence mapping is suitable to monitor the hologram without disturbing the on-going experiment. It's an in-situ measurement. After the measurement, defects are corrected by a feedback on the input hologram.

As a demonstration, we used our SLM to produce Laguerre-Gaussian beams in order to guide over a long distance a cold rubidium beam supplied by a 2D-MOT. We have strongly reduced the divergence of this source and thus increasing by a factor of 200 the atomic density after a propagation of 30 cm. Furthermore we showed that in such a guide the spontaneous emission is lower than in the usual red detuned gaussian guide case.

Inaugural Graduate Physics Student Association (GPSA) Talk (primarily meant for graduate students)
Monday, September 23, 2013
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "The First Determination of the Weak Charge of the Proton"

Emmanouil Kargiantoulakis , University of Virginia
[Host: GPSA]
ABSTRACT:
This general talk will give an overview of the very successful Standard Model (SM) of Physics, and the reasons that make us believe there is physics beyond it that we haven't discovered yet. This is the motivation for the Q_weak experiment in Jefferson Lab, that uses the violation of the parity symmetry to probe the weak interaction and test the SM predictions with high precision. The first results from the experiment constitute the first-ever determination of the proton's weak charge, the neutral-weak analog to the electric charge. The experimental measurement and the first results will be presented.
SLIDESHOW:
Atomic
Tuesday, August 6, 2013
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

## "Optical continuous-variable cluster states: theory and experiment"

Nicolas Menicucci , University of Sydney
[Host: Olivier Pfister]
ABSTRACT:
Cluster states are an entangled resource state that enable quantum computing using adaptive measurements alone. This is surprising when one considers what this means: one can quantum compute simply by *looking* at a quantum systems in a particular way! The continuous-variable incarnations of these states are simple to make using lasers and can be scaled up with ease. In this talk, I will describe the theoretical underpinnings of measurement-based quantum computation using continuous-variable systems, and I will report on their experimental realization, including the recent demonstration of a 10,000-mode (!) cluster state. Issues related to error correction and fault tolerance -- many of which remain open problems -- will also be discussed.
Atomic
Monday, April 15, 2013
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Ionization of Rydberg Atoms in Intense, Single-cycle THz Field"

Sha Li , University of Virginia
[Host: Bob Jones]
SLIDESHOW:
Atomic
Monday, April 1, 2013
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Metastable states in microwave ionization"

Alexandr Arakelyan , University of Virginia
[Host: Tom Gallagher]
ABSTRACT:
We report the excitation of metastable Li Rydberg atoms in the presence of a strong 38.3 GHz microwave field. We detect approximately 5% of the initial population in very high Rydberg states with n > 215 after the microwave pulse for a wide range of initial binding energies. The surviving population of atoms displays a periodic comb structure in energy with a periodicity matching the structure of the 38.3 GHz microwave field. A small static field displaces the entire comb to lower energy, and the high lying states disappear when the static field exceeds 30 mV/cm. We also perform measurements of microwave ionization thresholds in Li and, in spite of the fact that the pulse is 8000 cycles long, detect approximately 5% of the initial population in extremely high-lying states when the microwave pulse is subsequent to the laser excitation of a Rydberg state of any binding energy. We suggest that these atoms are trapped in metastable atom-field states during the microwave pulse and relax to the high-lying states when the field is turned off.
SLIDESHOW:
Atomic
Monday, March 25, 2013
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Quantum-wire cluster states in the quantum optical frequency comb"

Moran Chen , University of Virginia
[Host: Olivier Pfister]
SLIDESHOW:
Atomic
Monday, March 18, 2013
3:30 PM
Physics Building, Room 204
Note special time.

## "Applications & potentials of waveguide BEC interferometer: AC stark shift and free-fall revisited"

Tanwa Arpornthip , University of Virginia
[Host: Cass Sackett]
Atomic
Thursday, March 7, 2013
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

## "Information-efficient phase imaging using a single photon source"

Niranjan Sridhar , University of Virginia
[Host: Olivier Pfister]
Atomic
Thursday, February 28, 2013
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

Slideshow (PDF)

## "DFB Diode Laser Based Sensor for Isotope Ratio Detection of Methane using Continuous Wave Cavity Ring-down Spectroscopy"

Shaoyue Yang , University of Virginia
[Host: Kevin Lehmann]
SLIDESHOW:
Atomic
Thursday, February 21, 2013
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

Slideshow (PDF)

## "Low Field MRI of Laser Polarized Noble Gases"

Yuan Zheng , University of Virginia
[Host: Gordon Cates]
SLIDESHOW:
Atomic
Monday, February 18, 2013
3:30 PM
Physics Building, Room 204
Note special time.

## "Rydberg Wavepacket Evolution in an Ensemble of Cold Dipole-Dipole Coupled Atoms"

Tao Zhou , University of Virginia
[Host: Bob Jones]
Atomic
Monday, February 11, 2013
3:30 PM
Physics Building, Room 204
Note special time.

## "Generation of ultra-broadband entangled photons from chirped-MgSLT crystal: towards mono-cycle temporal entanglement generation"

Akira Tanaka , The Institute of Scientific and Industrial Research, Osaka University
[Host: Olivier Pfister]
ABSTRACT:
When the temporal correlation of two photons is compressed to the monocycle regime (3.56 fs, center wavelength: 1064 nm), one can expect new perspectives in quantum metrology, allowing applications such as submicron quantum optical coherence tomography and novel nonlinear optical experiments. For this aim, the two-photon state must essentially be ultra-broadband in the frequency domain and ultra-short in the time domain. In this seminar we report the successful generation of such ultra-broadband, frequency-correlated two-photon states via type-0, cw-pumped (532 nm) spontaneous parametric down conversion using four PPMgSLT crystals with different chirp rates of their poling periods. For the collinear condition, single-photon spectra are detected using a Si-CCD and an InGaAs photodiode array with a monochromator, while for a noncollinear condition, an NbN meander-type superconducting single photon detector (SNSPD) and an InP/GaAs photomultiplier tube (PMT) with a laser line Bragg tunable bandpass filter are used. The broadband sensitivity of the SNSPD and PMT in the near-infrared wavelength range enable singleshot observations with a maximum bandwidth of 820 nm among the four samples. Such spectra can in principle achieve a temporal correlation as short as 1.2 cycles (4.4 fs) with the use of appropriate phase compensation, which can be measured using the sum-frequency signal.
Special Atomic Seminar
Wednesday, November 28, 2012
2:00 PM
Physics Building, Room 210
Note special date.
Note special time.
Note special room.

## "Industrial Atomic Physics at Symmetricom"

Robert Lutwak , Symmetricom
[Host: Tom Gallagher]
Atomic
Monday, November 12, 2012
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "A Magnetometer and Gradient Magnetometer Atom Interferometer"

Frank Narducci , Naval Research Laboratory
[Host: Cass Sackett]
ABSTRACT:
We are currently developing atom interferometric techniques to measure magnetic fields and magnetic field gradients to high precision. In this talk, I will review the selection rules associated with driving the eleven Raman resonances in 85Rb atoms in an arbitrarily oriented magnetic field, and how to use polarization of the Raman fields to enhance or suppress desired transitions. I will then present the results of well-known “clock” transition interferometric measurements made in my laboratory in both the time domain and the frequency domain. I will then present and discuss similar measurements made on magnetically-sensitive transitions. The analogy between our measurement techniques and the famous Young’s double slit experiment will be highlighted. Finally, I will present the first measurements of interference from our gradient magnetometer.
SLIDESHOW:
Atomic
Friday, October 12, 2012
2:30 PM
Physics Building, Room 313
Note special date.
Note special time.
Note special room.

## "Realization of nonlinear interferometer and quantum correlated multiple beams using two four wave mixing amplifier in hot rubidium vapor "

Jietai Jing , East China Normal University
[Host: Olivier Pfister]
ABSTRACT:
I will report our recent progress for experimental generation of a nonlinear interferometer which has a visibility close to 1 and can result in an enhancement of phase sensitivity. We experimentally explored the possibilities for multiple quantum correlated beams generation from such a system.
Atomic
Monday, June 4, 2012
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "A Quantum Enhanced Gravitational Wave Detector"

Sheila Dwyer , MIT
[Host: Olivier Pfister]
ABSTRACT:
Advanced gravitational wave detectors, currently under construction, are expected to be limited by quantum optical noise in much of their detection band and using squeezed states of light is the most promising way to further improve their sensitivity. I will describe an experiment where squeezed light injection was used to reduce the shot noise limit in a 4 km long interferometric detector of the Laser Interferometer Gravitational-wave Observatory, leading to the best broadband sensitivity achieved to date in a gravitational wave detector.
SLIDESHOW:
Atomic
Monday, April 23, 2012
3:30 PM
Physics Building, Room 204
Note special time.

## "Continuous cavity ring down spectroscopy for ultra-sensitive detection of biological NO"

Vincent Kan , University of Virginia
[Host: Kevin Lehmann]
ABSTRACT:
Nitric oxide (NO) has received much attention in biochemistry and medicine as a physiologically active molecule involved in vasodilation and signal transduction. Determination of NO content in cells and tissues in the form of its S-nitrosothiol donor molecules is of great importance for medical diagnosis and treatment. We will report on our ongoing development of an instrument to measure trace levels of nitric oxide gas (NO), released from S-nitrosothiols after exposure to UV light (340 nm). The instrument uses the method of cavity ring-down spectroscopy, probing rotationally resolved lines in the vibrational fundamental transition near 5.2 μm. Preliminary spectroscopic measurements with an astigmatic multi-pass cell will also be reported.
Special AMO Seminar
Friday, April 20, 2012
10:00 AM
Physics Building, Room 313
Note special date.
Note special time.
Note special room.

## "Time Correlated Single Photon Counting Instrumentation and Applications Plus Photon Counting Detector Overview"

Nick Bertone & Michael Wahl , picoQuant GMbh
[Host: Olivier Pfister]
ABSTRACT:
Picoquant will present an overview of its technology based on Time Correlated Single Photon Counting. We will illustrate how this technology is used for Time-Resolved Analysis. Dr. Michael Wahl will present recent TCSPC advances in concept and technology leading to a new modular architecture allowing scalability in terms of the number of input channels, while using one common synchronization channel. Real-time sorting in hardware ensures delivering a single output data stream that contains time-tag records for all events from all inputs in correct temporal order, even at very high photon rates.

Nick Bertone from OEC will provide an overview on Photon Counting Detectors, this will include detectors with High Detection Efficiency, Fast timing resolution, Arrays and new developments.

Atomic
Monday, April 16, 2012
3:30 PM
Physics Building, Room 204
Note special time.

## "Using Symmetry to Reduce Noise in Measurements Made With a BEC Interferometer"

Robert Leonard , University of Virginia
[Host: Cass Sackett]
ABSTRACT:
The wave nature of matter provides us with the ability to construct atom interferometers. The strong nature of atom interactions coupled with the highly sensitive phase of matter-waves allows for the possibility of ultra high precision measurements. Unfortunately, noise introduced through vibrations in the apparatus currently limit the precision of our measurements. To reduce the affects of noise, I have been working to create a dual interferometer, which will consist of two identical interferometers running simultaneously. Using one interferometer as a reference, noise arising from vibrations can be removed.
Atomic
Monday, February 6, 2012
3:30 PM
Physics Building, Room 204
Note special time.

## "From Tom Gallagher's lab to Wall Street (almost)"

J. Veale, B. Anderson, W. Griffith, & D. Duncan , Lighthouse Instruments
[Host: Lauren Levac]
ABSTRACT:
This talk features four of Tom Gallagher's former students who took what they learned in graduate school and turned it into a successful Charlottesville-based technology company (Lighthouse Instruments). The talk will explore frequency modulation spectroscopy and its evolution over the last 20 years from the lab to a proven technology used in the manufacture pharmaceutical products. Frequency modulation spectroscopy is a high sensitivity form of laser absorption spectroscopy useful for gas phase measurements. The method was introduced to the pharmaceutical industry in the late 90's by Lighthouse and has found widespread adoption in R&D labs and manufacturing plants.
Atomic
Monday, December 19, 2011
11:00 AM
Physics Building, Room 313
Note special time.
Note special room.

## "Multiple Differential Study of Fragmentation Processes in 75 keV Proton – Molecular Hydrogen Collisions"

Kisra Egodapitiya , Missouri University of Science & Technology
[Host: Bob Jones]
Atomic
Tuesday, December 6, 2011
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

## "Interaction of low energy ions and electrons with surfaces of insulators"

Caixia Bu , University of Virginia
[Host: Raul Baragiola]
Atomic
Thursday, August 18, 2011
3:00 PM
Physics Building, Room 204
Note special date.
Note special time.

Slideshow (PDF)

## "Optical continuous-variable cluster states"

Nicolas Menicucci , Perimeter Institute for Theoretical Physics
[Host: Olivier Pfister]
ABSTRACT:
I will describe the theoretical underpinnings of one-way quantum computation using continuous-variable systems, as well as the pros and cons of several different methods of experimental implementation using lasers. Issues related to error correction and fault tolerance -- many of which remain open problems -- will also be discussed.
SLIDESHOW:
Atomic
Wednesday, August 10, 2011
2:00 PM
Physics Building, Room 204
Note special date.
Note special time.

## "Light storage under conditions of electromagnetically induced transparency and four wave mixing in a hot atomic vapor"

Nate Phillips , William and Mary
[Host: Bob Jones]
Atomic
Monday, June 27, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "'Enhancement of Rydberg Atom Interactions Using ac Stark Shifts"

Dr. Parisa Bohlouli-Zanjani , University of Waterloo
[Host: Tom Gallagher]
SLIDESHOW:
Atomic
Thursday, May 12, 2011
3:00 PM
Physics Building, Room 313
Note special date.
Note special time.
Note special room.

## "Fragmentation of small multi-electron molecular ions in cold electron collisions"

Dr. Julia Stützel , Max-Planck-Institute for Nuclear Physics
[Host: Bob Jones]
Atomic
Monday, May 9, 2011
3:30 PM
Physics Building, Room 313
Note special time.
Note special room.

## "Multipartite entanglement in the optical frequency comb of a depleted-pump optical parametric oscillator"

Reihaneh Shahrokhshahi , University of Virginia
[Host: Olivier Pfister ]
ABSTRACT:
The generation of massively entangled states is of great interest for quantum information. For quantum communication, multiparty quantum teleportation and quantum secret sharing are good examples. In this talk I will explain about the generation of multipartite continuous-variable entanglement in a single optical parametric oscillator (OPO) well above threshold. In this system, the multipartite entanglement is mediated between independent pairs of two-mode squeezed, bipartite entangled, OPO fields by way of the quantum dynamics of the strongly depleted pump field. We verify the multipartite nature of the entanglement by evaluating the van Loock-Furusawa inequalities.
Special Nuclear/HEP
Monday, April 25, 2011
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "The Investigation of Nucleon Structure at HERMES"

Morgan Murray , University of Glasgow
[Host: Simonetta Liuti]
SLIDESHOW:
Atomic
Monday, April 18, 2011
3:30 PM
Physics Building, Room 204
Note special time.

## "Bose-Einstein Condensate Interferometry and Applications to Rotation Sensing"

Robert Horne , University of Virginia
[Host: Olivier Pfister]
ABSTRACT:
Atom interferometry has proven a useful tool for precision measurements. In particular, our 87Rb condensate interferometer has been used to create a gyroscope. Our first generation experiment, while limited, has served as a proof of principle. We have made efforts to overcome these limits in our second generation design. Specifically, our linear interferometer is limited by vibrations and will likely limit the performance of our gyroscope. This is an issue that is being approached from multiple fronts, as will be discussed.
Atomic
Monday, April 11, 2011
4:00 PM
Physics Building, Room 204

## "Cooling of a diatomic molecule"

Edward Shuman , Yale University
[Host: Olivier Pfister]
ABSTRACT:
The development of laser cooling techniques to produce ultracold (T < 1mK) atoms has lead to rapid advances in a wide array of fields. Unfortunately, extending laser cooling to molecules has remained elusive. The primary problem is that laser cooling requires a large number ( > 104 ) of photon absorption/emission cycles. Molecules, however, have vibrational and rotational degrees of freedom, which typically lead to high branching probabilities into a large number of unwanted sublevels. Here we report on experiments demonstrating the laser cooling of a diatomic molecule which have overcome this problem. We use the molecule strontium monofluoride (SrF) where only three lasers and a magnetic field are necessary to scatter > 105 photons. We have demonstrated 1-D transverse cooling of a beam of SrF, dominated by Doppler or Sisyphus-type cooling forces depending on experimental parameters. We observe a reduction in the velocity distribution by a factor of 3 or more, corresponding to final 1-D temperature T < 1 mK. This transverse cooling may be useful for a variety of experiments; in addition, our results open a path to trapping and 3D cooling of SrF to the ultracold regime.
Atomic
Tuesday, February 1, 2011
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

## "Combing through earth and space: Broad bandwidth approaches to optical and infrared spectroscopy"

Scott Diddams , NIST
[Host: Olivier Pfister]
ABSTRACT:
An optical frequency comb based on the output of a mode-locked femtosecond laser can be a valuable tool in a variety of spectroscopic studies and applications. The frequency comb simultaneously provides excellent spectral resolution and broad wavelength coverage across the visible and near infrared. In this talk, I will describe our use of optical frequency combs for two emerging spectroscopic applications: (1) trace gas detection, and (2) calibration of astronomical spectrographs. In the first case, the output of a broadband frequency comb is used to directly measure the spectral fingerprint of an absorbing gas. A two-dimensional spectrometer permits rapid parallel readout over 5-10 THz with resolution limited ultimately by the comb element linewidth. Present efforts are aimed at adapting this approach for the 3-15 micron spectral region. The second class of applications involves using an atomically-stabilized frequency comb with large (>10 GHz) mode spacing to provide a precise calibration for astronomical spectrographs. We have focused our efforts on generating a comb in the 1550 nm range to be used in conjunction with a high-resolution spectrograph to search for earth-like planets around M-class stars.
Atomic
Monday, January 31, 2011
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Observation of shock waves and beyond luttinger liquid physics in cold atoms"

Manas Kulkarni , SUNY Stony Brook
[Host: Austen Lamacraft]
ABSTRACT:
I will present our work with experimentalists at Duke, involving the study of collisions between two strongly interacting atomic Fermi gas clouds. They observed exotic nonlinear hydrodynamic behavior, distinguished by the formation of a very sharp andstable density peak as the clouds collide and subsequent evolution into a box-like shape. We model the nonlinear dynamics of these collisions using quasi-1D hydrodynamic equations. Our simulations of the time-dependent density profiles show near perfect agreement with the data and provide clear evidence of shock wave formation in this universal quantum hydrodynamic system. We argue that these experiments on strongly interacting Fermi gases form an ideal playground for studying out-of-equilibrium nonlinear hydrodynamics. I will then talk about nonlinear collective field theory for a harmonically trapped two-component integrable model with inverse square interactions and spin-exchange. In this context, I will present several results such as spin-charge drag, gradient catastrophe, solitons all of which are hallmarks of physics beyond the luttinger liquid paradigm.
SLIDESHOW:
Atomic
Monday, October 25, 2010
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Polarizability of Rn-like Th4+ from Th3+ high-_L_ Rydberg states"

Mark Hanni , Colorado State University
[Host: Tom Gallagher]
SLIDESHOW:
Special Atomic Seminar
Friday, September 24, 2010
2:00 PM
Physics Building, Room 313
Note special date.
Note special time.
Note special room.

Slideshow (PDF)

## "Transport of Relativistic Electrons in a High Intensity Laser-Plasma Interaction"

Lee Elberson , University of Maryland and Lawrence Livermore National Lab
[Host: Bob Jones]
SLIDESHOW:
Atomic
Thursday, June 3, 2010
4:00 PM
Physics Building, Room 204
Note special date.

## "Excitation and acceleration of neutral atoms in strong laser fields"

Ulrich Eichmann , Max Born Institute, Berlin
[Host: Tom Gallagher]
Atomic
Monday, May 3, 2010
3:30 PM
Physics Building, Room 204
Note special time.

## "The observation of the electric field in an ultracold neutral plasma"

Hyunwook Park , University of Virginia
[Host: Lou Bloomfield]
Atomic
Monday, April 12, 2010
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "A tunable Bose-Einstein condensate in disordered potentials"

Giacomo Roati , LENS
[Host: Cass Sackett]
ABSTRACT:
We present our studies on a Bose-Einstein condensate (BEC) trapped in disordered potentials. The interactions between the atoms can be controlled at will thanks to a broad magnetic Feshbach resonance. The disorder is introduced into the system by means of a quasi-periodic lattice generated by superimposing two laser standing waves with incommensurate wavelengths. We study two different regimes. First, the interactions between the particles are tuned to zero. This ”ideal” gas in the bichromatic lattice reproduces the Aubry-Andr´e hamiltonian, which shows a transition between extended and exponentially localized single-particle wavefunction, similar to the Anderson model. We have directly observed the onset of localization by probing the momentum distribution and the absence of diffusion of the non-interacting condensate. In a second experiment, we reintroduce some repulsive interactions into the sample. In particular, we investigate the interplay between disorder and interactions. We observe the transition from incoherent Anderson localized states to fully coherent extended states. For large interactions the effect of the disorder is highly reduced and the system enters the BEC regime. The characterization of this superfluid to insulator transition (SIT) is particularly important. Infact, despite it is present in many different physical systems such as, for example, helium in porous media and high TC superconductors, its complete understanding is still missing.
SLIDESHOW:
Atomic
Monday, April 5, 2010
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Multimodal imaging device for intraoperative surgical guidance"

Kosta Popovic , University of Virginia
[Host: Lou Bloomfield]
SLIDESHOW:
Atomic
Monday, February 15, 2010
3:30 PM
Physics Building, Room 204
Note special time.

## "Novel Applications of Optical Pumping for Enhanced and Compact Sensors"

Krishna Myneni , US Army Research, Development and Engineering Command
[Host: Cass Sackett ]
ABSTRACT:
Optical pumping is a widely used technique in atomic physics for preparing desired angular momentum states of an ensemble of atoms. This technique is fundamental to the operation of many atom-based technologies, such as clocks, magnetometers, atom interferometry-based and NMR-based inertial sensors, and to the production of cold and ultracold atoms. We will discuss recent research by our group into two novel applications of optical pumping for sensor applications. The first involves the enhancement of conventional optical gyroscopes through the introduction of an intracavity resonant atomic medium. We have demonstrated, experimentally, that the steep and negative dispersion associated with an atomic vapor resonance may be used to enhance both the scale factor and the sensitivity of a Fabry-Perot cavity. We have also shown that optical pumping by a second laser may be used to continuously tune the response of the cavity. The second experiment involves use of optical hyperfine pumping to produce absorption resonances at frequencies of interest for laser cooling of atoms in sensors. In particular, we demonstrate that the hyperfine level structure of the Rb87 atom provides a naturally occuring pumping resonance which may be useful for locking the cooling laser in the production of optical molasses within compact cold-atom based sensors.
Atomic
Monday, November 30, 2009
3:30 PM
Physics Building, Room 204
Note special time.

## "ι dependence of autoionization rate in the weak static electric field"

Jirakan Nunkaew , University of Virginia
[Host: Lou Bloomfield]
ABSTRACT:
Dielectronic recombination (DR) is an important recombination process in the high temperature and astrophysical plasmas. In this talk we will show that it is possible to identify the energetically unresolved high ι states that contribute to DR by measuring the autoionization rate as a function of electric field. We measure the autoionization yields of the excited isotropic and anisotropic cores of Ba, 6p j nl, j=1/2, 3/2, ι >10 in the electric field and determine the highest ι such that the autoionization rate is equal to the radiative rate of Ba + 6p, AR=3.88×10 -9 .
Special Seminar
Friday, May 15, 2009
4:00 PM
Physics Building, Room 204
Note special date.

## "Entanglement in Open Quantum Systems"

Andreas Buchleitner , University of Freiburg
[Host: Tom Gallagher]
Special Seminar
Monday, May 11, 2009
4:00 PM
Chemistry Building, Room 304
Note special room.

## "EXPLORING ENZYMATIC ENERGY LANDSCAPE WITH SINGLE-MOLECULE SPECTROSCOPY"

YAN-WEN TAN , UNIVERSITY OF CALIFORNIA-BERKELEY
[Host: KEVIN LEHMANN]
ABSTRACT:
I use single-molecule optical microscopy to address a fundamental question in molecular biology: how does protein’s sequence encode its conformational dynamics and function? The model system that we study is the enzyme adenylate kinase (AK) from Escherichia coli. AK’s lid domain undergoes a large conformational change at the catalytic, millisecond timescale, which leads to a reasonable assumption that this lid dynamics is involved in AK’s enzymatic function; yet, its mechanistic roles and energetics remain elusive. Using the high-resolution time-dependent single-molecule FRET (Förster Resonance Energy Transfer) developed in our group, we have measured AK's lid movements on the millisecond scale and map out its entire conformational distribution along the FRET coordinate without a presumed model. Using these new pieces of information, we have quantitatively recovered AK's energetic landscape and related its stochastic lid dynamics to its catalytic function. Finally, the relationship between AK’s genetic coding and its catalytic function is experimentally established by introducing targeted mutation on specific AK sites. This study provides new perspectives on protein engineering.
Atomic
Wednesday, April 29, 2009
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

Slideshow (PDF)

## "Producing Photon-Pairs using non-linear optical waveguides"

Alexander Ling , NIST
[Host: Olivier Pfister]
ABSTRACT:
Correlated photon-pairs are a useful resource in obtaining heralded single photons or for the generation of entangled pairs of qubits. The workhorse method of generating photon-pairs has been Spontaneous Parametric Down-Conversion inside bulk nonlinear optical crystals. However, the emission profile of such photon-pairs is always multi-mode, and the overall coupling efficiency into single-mode optical fibers is poor. In order to enhance the coupling efficiency, it is desirable to produce photon-pairs inside engineered waveguide structures that have a higher degree of overlap with single-mode fibers. In this talk, I will present some of our recent work in generating and characterizing photon-pairs using two types of waveguides: a) a waveguide formed from periodically-poled KTP, and b) a photonic-crystal fiber (PCF). With the waveguide source, we have demonstrated photon-pair production via two different SPDC phase-matching methods (Type-0 and Type-II) from a single waveguide, and at the same temperature. I will also present the measured coincidence spectrum for the two phase-matching methods and discuss the differences between them. The PCF source generates photon-pair via Four-Wave Mixing, and is a more mature source compared to the PPKTP waveguide. We have been able to demonstrate the generation of photon-pairs that are indistinguishable, as well as polarization-entangled. In this talk I will describe our recent innovations to improve the coupling efficiency and stability of this source.
SLIDESHOW:
Atomic
Monday, April 20, 2009
4:00 PM
Physics Building, Room 313
Note special room.

## "Superconducting detectors for quantum information science and technology"

Sae Woo Nam , NIST
[Host: Olivier Pfister]
ABSTRACT:
There is increasing interest in using superconducting optical photon detectors in a variety of applications in quantum information science and technology. These applications require detectors that have extremely low dark count rates, high count rates, and high quantum efficiency. I will describe our work on two types of superconducting detectors, the Single Photon Superconducting Detector (SSPD) and superconducting Transition-Edge Sensor (TES). An SSPD is an ultra-thin, ultra-narrow (nm scale) superconducting meander that is current biased just below its critical current density. When one or more photon is absorbed, a hot spot is formed that causes the superconductor to develop a resistance and consequently a voltage pulse. By exploiting the sharp superconducting-to-normal resistive transtion of tungsten at 100mK, TES detectors give an output signal that is proportional to the cumulative energy in an absorption event. This proportional pulse-height enables the determination of the energy absorbed by the TES and the direct conversion of sensor pulse-height into photon number. I will discuss our results of using both of these new types of detector in quantum information applications and our progress towards developing detectors with quantum efficiencies approaching 100%.
Atomic
Monday, April 13, 2009
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Ultrashort Phase Locked Laser Pulses for Asymmetric Electric Field Studies of Molecular Dynamics"

Kelsie Betsch , University of Virginia
[Host: Lou Bloomfield]
SLIDESHOW:
Atomic
Wednesday, April 8, 2009
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

Slideshow (PDF)

## "Playing with quantum modes of light"

Claude Fabre , Universite Pierre et Marie Curie
[Host: Olivier Pfister]
ABSTRACT:
Multimode quantum systems have a high potential interest in many-qubit quantum computation, parallel quantum information processing and quantum metrology. We will show that some properties of multimode quantum states of light are 'intrinsic' , i.e. independent of the choice of the mode basis, and on the other hand that in many instances, it is very useful to identfiy particular modes that simplify the problem under consideration, such as the noise modes or the 'supermodes'. This will be illustrated by examples taken in the domains of 'quantum imaging' ( multi-transverse-mode quantum states) and 'quantum frequency combs' (multi-longitudinal-mode quantum states).
SLIDESHOW:
Atomic
Monday, March 23, 2009
4:00 PM
Physics Building, Room 313
Note special room.

## "The Superfluidity of Dipolar Fermi Gases"

Piotr Deuar , LPTMS
[Host: Cass Sackett]
ABSTRACT:
With the recent advances in cooling of heteronuclear dipolar molecules to their rovibrational ground state, the prospect of ultra-cold gases of fermionic dipoles in the lab is becoming realistic. Accordingly, the low energy collective excitations have been calculated for a uniform single-species polarized gas of fermionic dipoles below the superfluid critical temperature in the dilute BCS regime. Its behaviour differs strongly from the standard s-wave BCS gas due to a node line in its quasiparticle excitation spectrum that resembles that in the hypothetical polar phase of He-3 and exotic superconductors. One finds: (1) Appreciable damping of collective modes occurs even at T=0 and far below the sound velocity. (2) An aligned superfluid'' regime with no analogue in the s-wave-interacting gas, occurs for temperatures greater than the excitation energy. Here good quality superfluidity occurs only in directions concentrated broadly around the polarisation, whereas other directions are strongly damped. Furthermore, in the "good" direction, this aligned superfluidity is much less damped than at T=0.
Atomic
Monday, March 16, 2009
3:30 PM
Physics Building, Room 204
Note special time.

## "Guided Atom Interferometry with Thermal Atoms"

Alexey Tonyushkin , Harvard
[Host: Cass Sackett]
ABSTRACT:
Recent growth of the atom interferometry field is being driven by the wide array of its possible applications in precision measurements of the fundamental physical constants, and for sensing of inertial effects. Inertial sensing such as rotation was one of the first and one of the most practically important demonstrated applications for atom interferometers. Many believe that cold atom-based interferometer for rotational sensing – a device called a gyroscope – can be both compact and highly sensitive. In my talk, I review various types of atom interferometers and show that cold thermal atoms are well suited for atom interferometry. I will also talk about our recent implementation of a quantum kicked rotor, a system whose classical counterpart exhibits chaos, in a guided atom interferometer. I will discuss the applications of our quantum kicked rotor to accurate measurements of gravitational acceleration and atomic recoil frequency as well as to study a quantum-classical correspondence principle.
Atomic
Monday, November 10, 2008
3:30 PM
Physics Building, Room 204
Note special time.

## "Optical frequency combs with microwave repetition rates"

Danielle Braje , NIST
[Host: Olivier Pfister]
ABSTRACT:
Femtosecond laser frequency combs have intrinsic properties which make them enticing tools for modern laser physics: a broad frequency spectrum of more than an octave of bandwidth; a temporally short pulse width of several femtoseconds; an evenly spaced array of narrow frequency modes; and the ability to stabilize both the spacing and absolute position of the comb frequencies. These combined attributes make femtosecond combs a near perfect frequency standard or in essence, an ideal ruler for optical frequencies. A limitation of current state-of-the-art comb technology, however, stems from the closely spaced tics of this optical-frequency ruler. With typical frequency-modes spaced from 100 MHz to 1 GHz, individual comb lines are not readily distinguished. For applications such as high resolution spectrograph calibration, direct laser- frequency-comb spectroscopy, low-noise microwave generation, astronomy and optical waveform synthesis / fabrication, larger frequency mode spacing is necessary. I will discuss how current fs lasers may be tailored to overcome these limitations as well as other avenues for generation of widely spaced combs. In particular, I will focus on a novel, self-seeded monolithic resonator comb, which directly generates a 10 GHz comb. Through cascaded four-wave mixing (hyper- parametric oscillation), a cw-pumped, highly nonlinear fiber resonator cavity produces a comb that is centered at 1550nm with tailorable, mode spacing in the gigahertz range and spanning ∼ THz.
Atomic
Monday, October 27, 2008
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Interactions between Pairs of Cs Rydberg Atoms"

Richard Overstreet , University of Oklahoma
[Host: Tom Gallagher]
SLIDESHOW:
Atomic
Monday, October 13, 2008
3:30 PM
Physics Building, Room 204
Note special time.

## "Cold Rydberg atoms dynamics and ultracold plasmas in high magnetic "

Mudessar Shah , University of Michigan
[Host: Cass Sackett]
ABSTRACT:
We investigate cold Rydberg and plasmas in a particle trap that has the unique capability to simultaneously laser-cool and trap neutral atoms as well as to confine plasmas in magnetic fields of about three Tesla. The atom trap is a high-field Ioffe-Pritchard laser trap, while the plasma trap is a Ioffe-Penning trap that traps electrons and ions in separate wells. The observed plasma dynamics is characterized by a breathing-mode oscillation of the positive (ionic) plasma component, this feeds back on the behavior of the negative (electron) component of the plasma. At higher densities, the observed oscillations become nonlinear. The electron component has been found to undergo rapid cooling. We further report on the recombination of magnetized plasmas into Rydberg atoms in transient traps and quasi-steady-state traps. In transient traps, large numbers of recombined Rydberg atoms in high-lying states are observed. In quasi-steady-state traps, the measured numbers of recombined atoms are lower and the binding energies higher.
Atomic
Thursday, October 9, 2008
4:00 PM
Physics Building, Room 204
Note special date.

Slideshow (PDF)

## "ZEKE Rydberg states in a crowd and "Condensed Rydberg Clusters": A new state of matter?"

Klaus Muller-Dethlefs , University of Manchester
[Host: Tom Gallagher]
SLIDESHOW:
Atomic
Monday, September 15, 2008
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Introduction to AMO Physics"

Cass Sackett , University of Virginia
[Host: Lou Bloomfield]
SLIDESHOW:
Atomic
Tuesday, August 5, 2008
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

Slideshow (PDF)

## "Coherent manipulation of atomic wavefunctions in an optical lattice"

[Host: Cass Sackett]
ABSTRACT:
We present manipulations of a cloud of cold Sr 88 atoms in a vertical optical lattice potential. In particular we observe a resonant broadening of the atomic cloud by modulating the phase or the amplitude of the lattice potential. This broadening is caused by a resonant tunneling of an atomic wave functions between lattice cites. The width of the resonance spectra is determined only by the Fourier limit due to the absence of decoherence. This is experimentally confirmed up to 15 s of the modulation time. The small linewidth allows us to measure the local gravity with a sensitivity of 10 -6 g. We demonstrate stretching of an atomic wave function over a distance of 1 mm. Then atomic wave function can be refocused in controlled way, to a size close to initial.
SLIDESHOW:
Atomic
Friday, July 11, 2008
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.

Slideshow (PDF)

## "Cold Atom Interferometry for Gravitational Experiments"

Guglielmo Tino , LENS / Florence, Italy
[Host: Cass Sackett]
SLIDESHOW:
Atomic
Tuesday, May 20, 2008
11:00 AM
Physics Building, Room 204
Note special date.
Note special time.

## "Relativistic rescattering and multielectron ionization of atoms and molecules in strong and ultrastrong laser fields"

Sasikumar Palaniyappan , University of Delaware
[Host: Bob Jones]
Atomic
Monday, May 5, 2008
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Ultra-cold quantum gases for many-body physics and interferometry"

Seth Aubin , William and Mary
[Host: Cass Sackett]
ABSTRACT:
I will present the design and construction of an apparatus for generating an ultra-cold Bose-Fermi mixture of 87Rb and 40K on an atom chip at the College of William and Mary. In the near term, the apparatus will support experiments on degenerate fermion interferometry. In the long term, we are directing our efforts towards producing an ultra-cold gas of polar KRb molecules for investigating novel types of bosonic and fermionic superfluidity
SLIDESHOW:
Atomic
Monday, April 28, 2008
3:00 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Multiphoton microwave ionization of Li Rydberg atoms"

Josh Gurian , University of Virginia
[Host: Cass Sackett]
SLIDESHOW:
Atomic
Monday, April 14, 2008
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Phase Gradient Effects in a BEC Interferometer"

John Burke , University of Virginia
[Host: Cass Sackett]
SLIDESHOW:
Atomic
Monday, April 7, 2008
3:30 PM
Physics Building, Room 204
Note special time.

## "Continuous-Variable Entanglement with Concurrent Nonlinearities"

Matt Pysher , University of Virginia
[Host: Cass Sackett]
Atomic
Monday, February 18, 2008
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Optical frequency combs for stable radiation in the microwave, terahertz "

Qudsia Quraishi , Univ. of Colorado and NIST, Boulder
[Host: Olivier Pfister]
ABSTRACT:
Optical frequency combs (OFC) have dramatically changed the paradigm for precision optical frequency measurements. Modern precision measurements rely upon the comb to act as a frequency gear-work to bridge a reference frequency (microwave or optical) to another frequency of interest, which can result in 17 digits of measurement accuracy. For such frequency comparisons, which often span hundreds of nanometers, the noise contribution of the comb itself must be well understood. Additionally, beyond precision optical measurements, recent work has shown that very low phase noise microwave signals may also be extracted from OFCs. The limits to the combs' performance in the optical and microwave domains is a matter of current inquiry. In my talk, I will discuss noise properties associated with signals extracted from OFCs. In the case of the combs' optical signals, I will discuss the scaling of phase noise of OFCs across 240 nanometers of the combs' optical bandwidth. In the case of the combs microwave signals, I will discuss efforts currently underway to achieve very low phase noise signals, in the x-band range of 10 GHz, which exceed the performance of state-of-the-art microwave sources. Finally, I will discuss the integration of the comb with the terahertz domain to generate broadly tunable and narrow linewidth radiation in the terahertz regime.
SLIDESHOW:
Atomic
Monday, January 28, 2008
3:30 PM
Physics Building, Room 204
Note special time.

## "An A to Z of Applied Physics Programs at DARPA"

Jay Lowell , DARPA
[Host: Cass Sackett]
Atomic
Monday, January 21, 2008
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Scattering of Small Molecules by Surfaces"

Joseph R. Manson , Clemson University
[Host: Vittorio Celli]
ABSTRACT:
Scattering molecules from surfaces is one method of obtaining information about specific aspects of the molecule-surface interaction potential and about the exchange of energy between the various molecular degrees of freedom and the modes of surface excitation. Scattering experiments can also probe surface trapping and sticking and the initial precursors to chemical reactions. Many such experiments have been carried out using molecules with masses significantly heavier than hydrogen for which the translational and rotational degrees of freedom during the collision process can be approximated by classical mechanics. Described in this talk is a mixed classical-quantum theory of molecule-surface scattering that treats the translational and rotational motion of the molecule and the multiphonon excitation of the surface with classical mechanics while the internal molecular vibrational degrees of freedom are treated with quantum mechanics. Comparisons of calculations with recent experiments show that such a theory can be useful in explaining observed scattered angular distributions, translational energy-resolved spectra, energy transfer to molecular rotational modes, and excitation probabilities for internal vibrational modes.
SLIDESHOW:
Atomic
Monday, December 17, 2007
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Spectroscopic Manifestations of High-Rydberg Dynamics (Intra- and Intermolecular)"

Edward Grant , University of British Columbia
[Host: Tom Gallagher]
SLIDESHOW:
Atomic
Monday, October 15, 2007
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Towards Transient Laser Orientation of Diatomic Molecules"

Thibault Vogt , University of Virginia
[Host: Bob Jones]
ABSTRACT:
During the past ten years considerable attention has been devoted to the use of intense subpicosecond optical pulses to align and orient molecules (diabatic alignment and orientation). An intense pulse can give a momentum kick to the molecule, allowing for the creation of a rotational wavepacket and leading to periodic alignment and/or orientation. Although diabatic alignment was demonstrated several years ago, the ability to orient molecules using electric field pulses has yet to be proven experimentally. One possibility is to use an intense half-cycle pulse (terahertz radiation) which couples to the permanent dipole moment of a polar molecule (our case HBr). Another possibility is to overlap two electric laser field pulses with different optical frequencies (namely omega and 2*omega). In this seminar I will describe in more detail the different techniques for aligning and orienting molecules (static fields, laser fields) along with numerous possible applications in molecular and optical physics. I will also give an update on our recent computational and experimental efforts to achieve diabatic, field-free, orientation in the laboratory.
SLIDESHOW:
Atomic
Tuesday, September 25, 2007
5:00 PM
Physics Building, Room 204
Note special date.
Note special time.

## "Theory and applications of the truncated Wigner method for ultra-cold Bose gases"

[Host: Olivier Pfister]
ABSTRACT:
Following the great success of mean field theory in describing trapped Bose-Einstein condensates, there has recently been much interest in also including thermal and spontaneous processes which are not present in the mean field description. One way to do this involves using phase space methods which were developed in quantum optics to similarly extend the mean field theory of lasers. This talk will present an overview of theory and applications of the truncated Wigner method to ultra-cold Bose gas physics. We will cover the formal basis for the method, its connections to classical field methods and exact phase space methods, and discuss recent applications to a number of systems of experimental interest.
Atomic
Monday, September 24, 2007
3:30 PM
Physics Building, Room 204
Note special time.

## "Measurement of ac Stark Shift with a Guided Wave Interferometer"

Ben Deissler , University of Virginia
[Host: Cass Sackett]
Atomic
Monday, September 17, 2007
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "An Introduction to Atomic Physics"

Cass Sackett , University of Virginia
[Host: Cass Sackett]
SLIDESHOW:
Atomic
Monday, September 3, 2007
3:30 PM
Physics Building, Room 204
Note special time.

## "The Bloch Representation of Quantum States with D > 2"

Nicolas Menicucci , Princeton U. / U. of Queensland
[Host: Olivier Pfister]
ABSTRACT:
Quantum states are hard to visualize. This is true regardless of the system's dimension. Two cases are particularly nice, though: infinite-dimensional systems, for which quantum optics gives us the Wigner, P, and Q representations, and qubits, for which we can use the Bloch-vector representation. The Bloch picture can be generalized to states with finite dimension greater than two, but there are striking and important differences between the D = 2 and D > 2 Bloch pictures. This talk will introduce the Bloch representation of quantum states with D > 2 and will emphasize the similarities and differences as compared to the standard (qubit) case.
Atomic
Monday, May 7, 2007
3:30 PM
Physics Building, Room 205
Note special time.
Note special room.

## "The DARPA Quantum Network: Scaling beyond one photon in Boston"

Jonathan Habif , BBN Technologies
[Host: Olivier Pfister]
ABSTRACT:
The DARPA Quantum Network has entered its final phase of development under the Quantum Information Science and Technology (QuIST) program. The most recent successful demonstrations have included the integration of state-of-the-art photon detectors, development of custom high-speed electronics, and experimental production of entangled states of light. I will discuss the details of the most recent milestones in the quantum network, and describe the path forward for growing the network. Furthermore, I will discuss how quantum coherent technology developed under the QuIST program can be leveraged in other technological arenas.
Atomic
Monday, April 30, 2007
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Superradiance in cold Rydberg atoms"

Jianing Han , University of Virginia
[Host: Cass Sackett]
SLIDESHOW:
Atomic
Monday, April 16, 2007
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Time-Modulated Bright Beam Squeezing and Non-Gaussian States of Light"

Russell Bloomer , University of Virginia
[Host: Cass Sackett]
ABSTRACT:
Optical Parametric Oscillators are an excellent source of squeezed light. These squeezed states have a positive Wigner function and are Gaussian. For these states, there exist a limit to which the total squeezing spectrum can be reduced. We attempt to experimentally demonstrate the creation of squeezed states that exceed this limit of noise reduction by modulating the pump beam. These new squeezed will have a negative Wigner function and will be non-Gaussian. I will outline future experimental uses of this non-Gaussian light.
SLIDESHOW:
Atomic
Monday, April 9, 2007
3:30 PM
Physics Building, Room 204
Note special time.

## "OH Stark deceleration: magnetic trapping, molecular qubits, and cavity-assisted laser cooling"

Benjamin Lev , JILA
[Host: Cass Sackett]
ABSTRACT:
The experimental realization of large samples of ultracold, ground state polar molecules would be a major breakthrough for research in ultracold collisions and chemistry, quantum information processing, and the study of novel states of matter. To accomplish this goal, our research employs a Stark decelerator to slow a supersonic expansion of OH in its rovibronic ground state. At the decelerator's terminus, a 30 mK OH packet of density 10 4 cm -3 is caught and confined in a magnetic quadrupole trap. An adjustable electric field of sufficient magnitude to completely polarize the OH is superimposed on the trap in either a quadrupole or homogenous field geometry. The trap dynamics deviate from that governed by simple addition of the fields' forces on OH's magnetic and electric dipoles. Confinement of cold polar molecules in a magnetic trap, leaving large, adjustable electric fields for control, is an important step towards the study of low energy dipole-dipole collisions. The cold molecular packets produced via Stark deceleration have enabled us to perform precision microwave spectroscopy of the OH ground state structure, which serves as an important system for constraining variation of fundamental constants and for molecular quantum information processing. Future experiments will require much colder molecules, and we will briefly discuss prospects for cavity-assisted laser cooling of OH.
Atomic
Monday, April 2, 2007
3:30 PM
Physics Building, Room 204
Note special time.

## "Coherent Rydberg-Rydberg Collisions"

Mary Kutteruf , University of Virginia
[Host: Cass Sackett]
Special Colloquium
Monday, March 26, 2007
3:00 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Parity Violation and the Neutron"

Chris Crawford , LANL
[Host: Blaine Norum]
ABSTRACT:
Parity violation, discovered in 1957 in nuclear beta decay, is unique to the weak interaction. This property makes it possible to isolate weak contributions from the residual strong force, which dominates hadronic interactions by 7 orders of magnitude. The NPDGamma experiment is being carried out at Los Alamos National Laboratory to extract the weak pion-nucleon coupling by measuring the parity violating asymmetry in radiative neutron-proton capture with polarized neutrons to an accuarcy of 5x10-9. I will describe this experiment and give some prelimary results.
SLIDESHOW:
Atomic
Monday, March 19, 2007
3:30 PM
Physics Building, Room 204
Note special time.

Slideshow (PDF)

## "Physics with Atomic Clocks: Beyond What time is it?"

Kurt Gibble , Penn State University
[Host: Cass Sackett]
ABSTRACT:
Atomic clocks realize the most accurate measurements of any kind and are extremely sensitive to incredibly small perturbations. The current generation of atomic clocks uses laser-cooling and, after circumventing some new problems, these will realize 100 fold improvements in clock accuracies. I will describe the basic physics of clocks, the motivations for building better clocks, and several of the new problems. The new problems include frequency shifts due to collisions of the cold atoms, the size of the recoil of an atom when it absorbs a photon, and juggling many atoms in fountains. Looking forward, the next generation of atomic clocks will utilize optical frequency transitions. I will describe this elegant technology that allows us to count at optical frequencies (1015 Hz).
SLIDESHOW:
Atomic
Thursday, December 14, 2006
3:30 PM
Physics Building, Room 313
Note special date.
Note special time.
Note special room.

## "Universal Quantum Computation with Continuous-Variable Cluster States"

Nicolas Menicucci , Princeton University & University of Queensland
[Host: Olivier Pfister]
ABSTRACT:
I will report on work published in PRL 97, 110501 (2006), in which my co-authors and I describe a generalization of the cluster-state model of quantum computation to continuous-variable systems, along with a proposal for an optical implementation using squeezed-light sources, linear optics, and homodyne detection. For universal quantum computation, a nonlinear element is required. This can be satisfied by adding to the toolbox any single-mode non-Gaussian measurement, while the initial cluster state itself remains Gaussian. Homodyne detection alone suffices to perform an arbitrary multi-mode Gaussian transformation via the cluster state. We also propose an experiment to demonstrate cluster-based error reduction when implementing Gaussian operations.
Atomic
Monday, November 20, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "N/A"

Thanksgiving Recess , N/A
[Host: N/A]
Special Seminar
Monday, November 13, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "Alternative Careers for Physicists"

John McCune , SNL Financial
Atomic
Monday, November 6, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "Rings and Vortices in Matter Wave Experiments"

Chandra Raman , The Georgia Institute of Technology (Georgia Tech)
[Host: Cass Sackett]
ABSTRACT:
Quantum gases are rich systems that possess many parallels with condensed matter. Atomic physicists can avail themselves of many tools for shaping these gases and tailoring their properties. For example, one can create beautifully ordered lattices of quantized vortices within a Bose-Einstein condensate (BEC) by magnetic or optical "stirring" of the gas, similar to those observed in superconductors and liquid helium-3. In our laboratory at Georgia Tech we have used Bragg scattering to probe the momentum distribution of arrays of these vortices. In addition, I will also discuss our efforts to use optical forces to tailor the matter wave expansion of a BEC, with applications to atom optical focusing and guiding.
Atomic
Monday, October 30, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "An Overview of Atomic Clocks"

Amber Post , University of Virginia
[Host: Cass Sackett]
Atomic
Monday, October 9, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "N/A"

[Host: N/A]
Atomic
Monday, September 25, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "Probing Dissociation Dynamics through a Conical Intersection in Ammonia"

Russell Minns , University of Virginia
[Host: Cass Sackett]
Atomic
Monday, September 11, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "An Introduction to AMO Physics"

Cass Sackett , University of Virginia
[Host: Cass Sackett]
Atomic
Monday, September 4, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "An Introduction to AMO Physics"

Cass Sackett , University of Virginia
[Host: Cass Sackett]
Atomic
Monday, April 24, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "NRL's Effort on Magnetic Guiding and Manipulation Using Atom-Chip and Permanent Magnets"

Eun Oh , Naval Research Laboratory
[Host: Cass Sackett]
Atomic
Monday, April 17, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "Probing Time-Dependent Electron Interaction in Doubly-Excited Electron Wave Packets"

Xiangdong Zhang , UVA
[Host: Cass Sackett]
Atomic
Monday, April 10, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "Atom Interferometry with Bose-Einstein Condensates"

Ben Deissler , UVA
[Host: Cass Sackett]
Atomic
Monday, April 3, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "Microwave Ionization of Sodium at High Scaled Frequency"

Xiaodong Zhang , UVA
[Host: Cass Sackett]
Atomic
Monday, March 27, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## ""RESERVED""

"RESERVED" , "RESERVED"
[Host: JKG/SACKETT]
Atomic
Monday, March 20, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "Metal Cluster Magnetism"

Wei Jiang , UVA
[Host: Cass Sackett]
Atomic
Monday, February 27, 2006
3:30 PM
Physics Building, Room 204
Note special time.

## "TBA"

RESERVED , UVA
[Host: JKG]
Atomic
Monday, December 5, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Revisiting the Core Polarization Model"

Ed Shuman , UVA
[Host: Thomas Gallagher]
Atomic
Monday, November 28, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "The Schwinger Representation (or second-quantized Bloch sphere) and Quantum Interferometry"

Olivier Pfister , UVA
[Host: Cass Sackett]
Atomic
Monday, October 31, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Continuous Variables in Qubits and Qudits: What's the Difference?"

Olivier Pfister , UVA
[Host: Cass Sackett]
Atomic
Monday, October 10, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Battling Decoherence in Rydberg Quantum Bits"

Russell Minns , UVA
[Host: Bob Jones]
Special Atomic Seminar
Thursday, September 29, 2005
4:00 PM
Physics Building, Room 313
Note special date.
Note special room.

## "Ultracold Neutral Plasmas"

Thomas Pattard , Dresden
[Host: Thomas Gallagher]
ABSTRACT:
Recent advances in trapping and cooling of neutral atomic gases have permitted achieving ultralow temperatures far below 1K. With this, a wealth of new research fields has opened up, not at all limited to the realization of Bose Einstein condensation and related questions. In this talk, I will introduce one of these research topics, namely the physics of ultracold neutral plasmas. The fact that the plasma is many orders of magnitude colder than "conventional" plasmas leads to some remarkable properties, akin to conditions realized in exotic astrophysical environments. A theoretical description of these systems relies on methods and concepts bridging the gap between traditional atomic physics, plasma physics and nonequilibrium thermodynamics. On the other hand, this also means that the study of cold plasmas can provide new stimulus for all of these fields.
Atomic
Monday, September 19, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Bose-Einstein Condensation and Atom Interferometry"

Jessica Reeves , UVA
Atomic
Monday, September 5, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Introduction and Atomic Units"

Cass Sackett , UVA
Atomic
Monday, August 1, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Entanglement Conditions for Two and Three Mode States"

Mark Hillery , Hunter College at the City University of New York
[Host: Olivier Pfister]
ABSTRACT:
This will be a chalkboard talk based on very recent work of the author and Suhail Zubairy from Texas A&M (see http://arxiv.org/abs/quant-ph/0507168 for more details) about finding new ways of detecting entanglement, with connections to experimental physics.
Atomic
Monday, May 2, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "The Zel'dovich Effect and Evolution of Atomic Rydberg Spectra Along the Periodic Table"

Mike Timmins , UVA
ABSTRACT:
In 1959 Ya. B. Zel'dovich predicted that the bound-state spectrum of the non-relativistic Coulomb problem distorted at small distances by a short-range potential undergoes a peculiar reconstruction whenever this potential alone supports a low-energy scattering resonance. However documented experimental evidence of this effect has been lacking. Previous theoretical studies of this phenomenon were confined to the regime where the range of the short-ranged potential is much smaller than Bohr's radius of the Coulomb field. We go beyond this limitation by restricting ourselves to highly-excited s states. This allows us to demonstrate that along the Periodic Table of elements the Zel'dovich effect manifests itself as systematic periodic variations of the Rydberg spectra with a period proportional to the cubic root of the atomic number. This dependence, which is supported by analysis of experimental and numerical data, has its origin in the binding properties of the ionic core of the atom.
Special Seminar
Tuesday, April 26, 2005
4:00 PM
Physics Building, Room 313
Note special date.
Note special room.

## "A Cold Atom Electron Source"

Edgar Vrendenbregt , Eindhoven University of Technology - The Netherlands
[Host: Thomas Gallagher]
Atomic
Monday, April 25, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Production of Non-classical Light of Squeezed State by OPA"

Daruo Xie , UVA
[Host: Olivier Pfister]
Atomic
Monday, April 18, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "New Impulse Momentum Retrieval Techniques and Measurements"

Jeremy Murray-Krezan , UVA
[Host: Robert Jones]
Atomic
Monday, April 11, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Dipole-dipole and van der Waals Interactions in Frozen Rydberg Gases"

Paul Tanner , UVA
[Host: Tom Gallagher]
Atomic
Monday, March 28, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "The Two-photon Raman Laser"

Olivier Pfister , UVA
Atomic
Monday, March 21, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "The Stark Effect"

Robert Jones , UVA
Atomic
Monday, March 14, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Ultra-high Resolution Molecular Spectroscopy: Hyperfine Interactions and Internal Symmetry Breakings"

Olivier Pfister , UVA
Cancelled due to snow - rescheduled for 03/21/05.
Monday, February 28, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "The Stark Effect"

Bob Jones , UVA
Atomic
Monday, February 21, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "TBA"

AVAILABLE
Special CM Seminar
Monday, February 14, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "The Nernst Effect in High-temperature Superconductors"

Iddo Ussishkin , Minnesota
[Host: Paul Fendley]
ABSTRACT:
One of the puzzles of high-temperature superconductivity concerns the nature of the non-superconducting state above the critical temperature T_c. Recently, a measurement of the Nernst effect, a transverse thermoelectric response, revealed an anomalously large Nernst signal above T_c which is very different from that observed in conventional materials. In this talk, I discuss the theory of the Nernst effect in the cuprates. I will argue that at least in a part of the phase diagram, corresponding to the overdoped cuprates, the puzzle can be explained within the theory of superconducting fluctuations. For the underdoped case, I will consider the limitations set by the Nernst effect measurements on possible theoretical scenarios.
Atomic
Monday, February 7, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Multipartite Continuous Variable Entanglement Using Concurrent Nonlinearities"

Raphael Pooser , UVA
[Host: Olivier Pfister]
Atomic
Monday, January 31, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "TBA"

AVAILABLE
Joint Seminar - Atomic/Condensed Matter
Monday, January 24, 2005
3:30 PM
Physics Building, Room 204
Note special time.

## "Phases of Rotating Bosons"

Kareljan Schoutens , University of Amsterdam
[Host: Paul Fendley]
ABSTRACT:
We discuss states of matter that arise when ultra-cold, Bose-condensed atoms are made to rotate. For not-too-high rotation, triangular vortex lattices have been observed. We discuss the nature of similar lattices for the case of bosons with 2 or 3 degenerate components. We also discuss the atomic quantum Hall states that are expected to form after a quantum melting of the vortex lattice at ultra-high rotation, and present experimental signaturesof such states.
Atomic
Monday, January 17, 2005
11:00 AM
Physics Building, Room 204
Note special time.

## "Non-holonomic Control and Coherence Protection by the Zeno Effect "

Vladimir Akulin , Laboratoire Aime Cotton - Orsay, France
[Host: Thomas Gallagher]
Atomic
Monday, December 6, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Photodetachment From Trapped Ions in External Fields"

John Yukich , Davidson College
[Host: Cass Sackett]
ABSTRACT:
What are negative ions, and why should we be interested in them? And what is photodetachment? In this talk I briefly present some of the pertinent background to negative ions and the field of photodetachment dynamics. I will then describe several experiments spanning the areas of continuum electron wavepackets, detachment in external electric and magnetic fields, and precision detachment spectroscopy.
Atomic
Monday, November 29, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Multipartite Continuous-Variable Entanglement From Concurrent Nonlinearities"

Olivier Pfister , UVA
Atomic
Monday, November 22, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Generation of Multipartite Entangled States and its Applications "

Jietai Jing , UVA
[Host: Olivier Pfister]
Atomic
Monday, November 15, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "High-Harmonic Generation in Gases"

Bob Jones , UVA
Atomic
Monday, November 15, 2004
4:00 PM
Physics Building, Room 204

## "HHG in Hollow Core Waveguides: Phase-Matching and Molecular Alignment Effects"

Bret Sickmiller , UVA
[Host: Bob Jones]
Atomic
Monday, November 8, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Cluster Electronic Dynamics"

Songbai Ye , UVA
[Host: Lou Bloomfield]
Atomic
Monday, November 8, 2004
4:00 PM
Physics Building, Room 204

## "Magnetism in Clusters"

Forrest Payne , UVA
[Host: Lou Bloomfield]
Atomic
Monday, October 25, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Molecular Dynamics in Intense Laser Fields"

Bob Jones , UVa
Atomic
Monday, October 25, 2004
4:00 PM
Physics Building, Room 204

## "Transient Molecular Alignment"

Dan Pinkham , UVa
Atomic
Monday, October 18, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Rydberg Wavepackets"

Tom Gallagher , UVA
Atomic
Monday, October 4, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Feedback and Servos"

Lou Bloomfield , UVA
Atomic
Monday, September 27, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Classical Manipulation of Rydberg Atoms"

Haruka Maeda , UVA
[Host: Cass Sackett]
Atomic
Monday, September 13, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "The Two - Level Atom"

Cass Sackett , University of Virginia
Atomic
Thursday, August 5, 2004
4:00 PM
Physics Building, Room 313
Note special date.
Note special room.

## "New Aspects in Detention and Formation of Ultracold Molecules"

Goran Pichler , Institute of Physics, University of Zagreb
[Host: Tom Gallagher]
Tuesday, May 18, 2004
2:00 PM
Physics Building, Room 204
Note special date.
Note special time.

## "Characterization of the transient behaviour in a colliding pulse mode locked laser"

Wei Yang , College of William & Mary
[Host: Thomas Gallagher]
Atomic
Monday, April 26, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "A New Type Of Interferometer Using BEC"

Ofir Garcia , UVA
[Host: Paul Fishbane]
Atomic
Monday, April 19, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "BEC: Production: How To make A Condensated"

Jessica Reeves , UVA
[Host: Olivia Pfister]
Atomic
Monday, April 5, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Quantum error Correction With continuous Variables"

Richard Barnes , UVA
[Host: Olivier Pfister]
Atomic
Monday, March 29, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Atom Interferometry & Pulse Diffusion"

Cass Sackett , University of Virginia
[Host: Paul Fishbane]
Atomic
Monday, March 22, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "The Second-quantized Bloch Sphere: The Schwinger Representation"

Olivier Pfister , UVA
[Host: Olivier Pfister]
Atomic
Monday, March 15, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "The Bloch Sphere"

Cass Sackett , UVA
[Host: Cass Sackett]
Atomic
Monday, February 16, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Ultrastable lasers and optical parametric oscillators"

Olivier Pfister , UVA
[Host: Olivier Pfister]
Atomic
Monday, February 9, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Chaos induced pulse trains in the Ionization of Hydrogen"

Kevin Mitchell , College of William & Mary
[Host: Bob Jones]
34th Annual Hoxton Lecture
Monday, February 9, 2004
7:00 PM
Physics Building, Room 203
Note special time.
Note special room.

## "Ultra-Precise Laser Spectroscopy: Counting the Ripples of a Light Wave"

Professor Theodor Hansch , Director of Max Panck Institute
[Host: Department of Physics]
Atomic
Monday, February 2, 2004
3:30 PM
Physics Building, Room 204
Note special time.

## "Electronic Wavepackets"

Bob Jones , UVA
[Host: Olivier Pfister]
Atomic
Thursday, January 22, 2004
4:00 PM
Physics Building, Room 204
Note special date.

## "Ultra-Intense Field Physics:Atomic Response"

Enam Chowdhury , University of Delaware
[Host: Bob Jones]
ABSTRACT:
There is a paradigm shift from high fields (below ~1016 W/cm2) to ultra-high fields, in terms of basic atomic response to the light field. Electron motion becomes relativistic, dipole approximation breaks down, magnetic fields of the light play an important role. What happens to an atom/ion in such an intense field? How are electron correlation effects (e.g. 2 electron wave-packet dynamics) modified? I will try to shed light on some of these topics. Also, I will discuss some novel techniques that we have developed to facilitate the achievements of such fields in table top experiments.
Atomic
Monday, December 1, 2003
3:30 PM
Physics Building, Room 204
Note special time.

## "Heisenberg-limited interferometry with twin boson modes: not such a bad idea after all..."

Olivier Pfister/Raphael Pooser , UVA
[Host: Cass Sackett]
ABSTRACT:
In this talk, we'll introduce the fundamental limits to interferometric (and spectroscopic) measurements and discuss the particular technique of Bayesian twin-mode interferometry, introduced by Holland and Burnett [1,2]. We will present new results of numerical simulations that show that, contrary to what had been predicted thereafter [3], experimental feasibility is quite promising, indeed.

[1] M.J. Holland and K. Burnett, Phys. Rev. Lett. 71, 1355 (1993). [2] T. Kim, O. Pfister, M.J. Holland, J. Noh, and J.L. Hall, Phys. Rev. A 57, 4004 (1998). [3] T. Kim, Y. Ha, J. Shin, H. Kim, G. Park, K. Kim, T.-G. Noh, C.K. Hong, Phys. Rev. A 60, 708 (1999).

Atomic
Monday, November 24, 2003
3:30 PM
Physics Building, Room 204
Note special time.

## "Non dispersing Wave packets"

Thomas Gallagher/Haruka Maeda , UVA
[Host: Cass Sackett]
Atomic
Monday, November 10, 2003
3:30 PM
Physics Building, Room 204
Note special time.

## "Multi-Photon Processes"

Bob Jones , UVA
[Host: Cass Sackett]
Atomic
Monday, November 3, 2003
3:30 PM
Physics Building, Room 204
Note special time.

## "Multi-Photon Processes"

Bob Jones , UVA
[Host: Cass Sackett]
Atomic
Monday, October 13, 2003
3:30 PM
Physics Building, Room 204
Note special time.

## "Excitation routes and ionization dynamics of two-electron atoms in laser fields"

Uli Eichman , Max Born Institute in Berlin
[Host: Cass Sackett]
Atomic
Monday, October 6, 2003
3:30 PM
Physics Building, Room 204
Note special time.

## "Quantum Interference of Ultrastable Twin Beams"

Olivier Pfister and Sheng Feng , UVA
[Host: Cass Sackett]
Atomic
Monday, September 29, 2003
3:30 PM
Physics Building, Room 204
Note special time.

## "Resonant Energy Transfer Among Rydberg Atoms"

Thomas Gallagher and Wenhui Li , UVA
[Host: Cass Sackett]
Atomic
Monday, September 15, 2003
3:30 PM
Physics Building, Room 204
Note special time.

## " Bloomfield - A Brief Introduction to Magnetism in Clusters of Atoms. Payne - Considerations in the Development of an Atomic Cluster Source"

Louis Bloomfield and Forrest Payne , UVA - Department of Physics
[Host: Cass Sackett]
Atomic
Monday, September 8, 2003
3:30 PM
Physics Building, Room 204
Note special time.

## "Sackett: Saturated Absorption Spectroscopy and Laser Frequency Locks and Jessica Reeves: Stable Operation of a Dichroic Atomic Vapor Laser Lock"

Cass Sackett and Jessica Reeves , UVA
[Host: Cass Sackett]
Atomic
Monday, September 1, 2003
4:00 PM
Physics Building, Room 204

## "Things You Should Pay Attention To As A Graduate Student in AMO Physics"

Cass Sackett , UVA - Department of Physics
[Host: Cass Sackett]
Atomic
Monday, April 28, 2003
4:00 PM
Physics Building, Room 204

## "Generation of Nonclassical Light States with An Ultrastable Optical Parametric Oscillator"

Sheng Feng , UVA
[Host: Bob Jones]
Atomic
Monday, April 21, 2003
4:00 PM
Physics Building, Room 204

## "Introduction to Nonclassical Light"

Olivier Pfister , UVA
[Host: Robert Jones]
SPECIAL ATOMIC SEMINAR
Monday, April 14, 2003
2:30 PM
Physics Building, Room 210
Note special time.
Note special room.

## "Molecules in Non-Perturbative Laser Fields: Dynamics and Control"

[Host: Bob Jones]
Atomic
Monday, April 7, 2003
4:00 PM
Physics Building, Room 204

## "A Bose-Einstein condensate in optical lattices: study of a quantum gas in reduced dimensionalities"

Bruno Laburthe-Tolra , NIST
[Host: Thomas Gallagher]
Atomic
Monday, October 21, 2002
4:00 PM
Physics Building, Room 204

## "TBA"

Mike Chapman , Georgia Tech
[Host: Cass Sackett]
Atomic
Monday, October 7, 2002
4:00 PM
Physics Building, Room 204

## "Interferometric detection of gravitational waves: technical issues and Challenges"

Francois Bondu , CNRS-Observatoire De La Cote Dazur
[Host: Olivier Pfister]
ABSTRACT:
The detection of gravitational waves, predicted by general relativity, requires to detect the relative motion between masses at rest. An interferometric setup such as the one selected by VIRGO (project between France and Italy) or LIGO (US observatory) should have the required sensitivity to see severe astrophysical events. This requires to be able to control seismic noise, the thermal noise of the masses, the frequency noise of the laser, the shot noise on the photodiode detector, and to have high specifications on the mirrors (roughness, losses). Advanced interferometers will call for even advanced technologies: squeezed light, cryogenic mirrors, all reflective optical setups, advanced seismic isolations...
Atomic
Monday, May 13, 2002
4:00 PM
Physics Building, Room 313
Note special room.

## "Laser Processing of Films: From High Tc Superconducting Films to Engineered Tissue Constructs"

Doug Chrisey , US Naval Research Laboratory, Washington, D. C.
[Host: Ian Harrison]
Atomic
Monday, March 18, 2002
4:00 PM
Physics Building, Room 204

## "Microwave Spectroscopy of Cold Rydberg Atoms"

Wenhui Li , University of Virginia
[Host: L. Bloomfield]
Atomic
Monday, November 12, 2001
3:30 PM
Physics Building, Room 313
Note special time.
Note special room.

## "BEC...With a View Towards Neutral - Atom Quantum Information Processing"

Brian King , NIST
[Host: Cass Sackett]
Atomic
Monday, October 15, 2001
3:30 PM
Physics Building, Room 313
Note special time.
Note special room.

## "Strong-Field Chemistry: Teaching Lasers to Selectively Break and Make Bonds"

Robert Levis , Wayne State Univ.
[Host: Robert Jones]
Atomic
Wednesday, July 11, 2001
4:00 PM
Physics Building, Room 204
Note special date.

## "Imaging Dissociating Metastable He2+2"

Itzik Ben-Itzhak , J. R. Macdonald Laboratory, Kansas State University
[Host: Robert Jones]
Atomic
Monday, July 9, 2001
4:00 PM
Physics Building, Room 204

## "Effect of the interactions in the Bose Einstein condensation of gases"

Frank Laloe , Ecole Normale Superieure
[Host: Peter Arnold]
Atomic
Monday, April 30, 2001
4:00 PM
Physics Building, Room 204

## "Photoelectron Diffraction Mapping: Molecules Illuminated from Within"

Allen Landers , Western Michigan
[Host: Bob Jones/Eric Wells]
ABSTRACT:
Much of our knowledge of the internal structure of matter results from the scattering and diffraction of electrons or X-rays. In many cases, the matter under investigation is in crystalline (or absorbate) form and can therefore be easily oriented in the laboratory. However, there are fundamental questions that may only be addressed through the direct study of single atoms or molecules (i.e. gas phase). It is therefore important that we seek methods which allow the detailed exploration of the orientation dependence of otherwise randomly oriented systems. I will discuss the use of a multiparticle coincidence technique to image the diffraction of an electron wave whose source is a specific site in a free molecule, i.e. core-level photoelectrons are used to illuminate the molecule from within. By choosing photons (and therefore photoelectrons) of appropriate energy, we can cause the photoelectron to resonate as it emerges through the molecular potential. This results in a richly structured electron diffraction pattern in the body-fixed frame of the randomly oriented molecule in the gas phase, and ultimately provides a unique "fingerprint" of the molecular potential.
Atomic
Monday, April 16, 2001
4:00 PM
Physics Building, Room 204

## "Subthreshold photoionization in molecular dopant/perturber systems"

Cherice Evans , Louisiana State University
[Host: Thomas Gallagher]
Atomic
Monday, March 19, 2001
4:00 PM
Physics Building, Room 204

## "Stair-Step Decay of Autoionizing Wavepackets"

Santosh Pisharody , University of Virginia
[Host: O. Pfister]
Atomic
Monday, February 19, 2001
4:00 PM
Physics Building, Room 204

## "Atomic Coherence in Multi-Level Atomic Systems and Its Applications"

Min Xiao , Univ. of Arkansas
[Host: Olivier Pfister]
ABSTRACT:
Atomic coherence effects in multi-level atomic systems, such as electromagnetically induced transparency and enhanced dispersion with reduced absorption, will be presented. I will discuss some interesting applications of such atomic coherence effects in nonlinear optical processes and group velocity reduction in such media.
Atomic
Monday, February 12, 2001
4:00 PM
Physics Building, Room 204

## "Probing the Momentum Distribution of Continuum Wavepackets Using Electron - Ion Recombination"

Jason Ziebel , University of Virginia
[Host: Olivier Pfister]
ABSTRACT:
We have used ultrashort, nearly unipolar "half cycle" electric field pulses (HCPs) as a tool to measure the time-dependent momentum distribution of electrons in a Stark induced continuum. Ca atoms in an external field are excited from the ground state into an intermediate 4s4p state with a nanosecond dye laser. A 1 ps laser pulse with a bandwidth of approximately 20cm-1 promotes the 4s4p atoms to the field induced continuum, with an energy just above the saddle point in the Stark potential. At a variable time delay Delta-t following the excitation of the continuum wavepacket, the system is exposed to a HCP which imparts a non-zero linear momentum "kick". The portion of the probability distribution moving antiparallel to the applied kick suffers a reduction in its total energy. The fraction of probability amplitude whose energy is below the saddle-point forms a bound wavepacket. Because the recombination probability depends on the kick strength and distribution of momentum along the kick direction, the time-dependent momentum distribution of the continuum wavepacket can be recovered from measurements of recombination probabilities versus kick strength, orientation of the momentum kick, and time delay Delta-t.
Atomic
Monday, December 11, 2000
4:00 PM
Physics Building, Room 204

## "Atoms See the Light: Making Molecules From Ultracold Atoms"

Frederick Fatemi , NIST
[Host: Thomas Gallagher]
ABSTRACT:
Photoassociation, the process by which two free atoms absorb a photon to form a bound, excited molecule, is an extremely powerful tool for studying long-range atom-atom interactions. In a sample of trapped, ultracold (T < 1 mK) atoms, the technique is most often used to obtain high resolution spectroscopy of electronically-excited molecules near their dissociation limit. However, we have recently used this technique to monitor and manipulate collisions of ultracold atoms, and to produce weakly bound, translationally cold molecules in their electronic ground state. I will discuss some of these recent interesting results from the Laser Cooling and Trapping Group at NIST.
Atomic
Monday, November 27, 2000
4:00 PM
Physics Building, Room 204

## "Formation of ultra cold cesium molecules through photoassociation"

Laburthe Bruno , Laboratoire Aime Cotton, CNRS Orsay France
[Host: Tom Gallagher]
Atomic
Monday, November 13, 2000
4:00 PM
Physics Building, Room 204

## "Photoelectron Spectroscopy of Alkali-Halide by Andy Dally and Magnetic Properties of Clusters by Hongtao Zhang "

Andy Dally & Hontao Zhang , UVA
Atomic
Monday, October 16, 2000
4:00 PM
Physics Building, Room 204

## "Electronic Structures and reactions of transition-metal-cluster ions"

Akira Terasaki , Cluster Research Laboratory, Toyota Technological Institute
[Host: Louis Bloomfield]
ABSTRACT:
From recent extensive studies on atomic and molecular clusters, it has been shown that their physical and chemical properties alter dramatically as a function of the number of constituent atoms (cluster size). Particularly, clusters of transition-metal elements attract attention because they are expected to possess novel characters in magnetism and catalysis. Since these properties originate from the electronic and geometric structures, it is essentially important to investigate their structures by both experimental and theoretical studies. From the experimental side, the laser spectroscopy of size-selected cluster ions is one of the most powerful means for this purpose. From the theoretical side, on the other hand, recent advances in density-functional theory (DFT) provide powerful tools to search for the optimized geometry and to calculate the electronic structures of small clusters. The theoretical approach to the analysis of the experimental results allows understanding of the size-specific properties of those clusters. On the basis of this strategy we have carried out photoabsorption and photoelectron spectroscopies of small cluster ions of cobalt, vanadium and manganese. Discussion is made by focusing on their magnetic properties. Regarding reactivity, our recent experiments on the reaction of nickel cluster ions with a methanol molecule have revealed reaction processes clearly dependent on the cluster size.
Atomic
Monday, September 25, 2000
4:00 PM
Physics Building, Room 204

## "Collision physics with a laser-prepared target"

Brett DePaola , Kansas State University
[Host: Bob Jones]
Atomic
Monday, April 24, 2000
4:00 PM
Physics Building, Room 204

## "Spontaneous Evolution of Rydberg Atoms to a Cold Plasma"

Michael Robinson , University of Virginia
Atomic
Monday, April 17, 2000
4:00 PM
Physics Building, Room 204

## "Probing Excited States of Ultracold Molecules Using Photoassociative Spectroscopy"

James P. Shaffer , The National Research Council, The Steacie Institute for Molecular Sciences, Ottawa, ON, Canada
[Host: Robert Jones]
ABSTRACT:
We describe the spectroscopy of highly excited states of ultracold molecules. We use a new photoassociative approach based on resonantly enhanced multiphoton ionization to probe these systems. We excite a large number of rotational states which provides a rich rovibrational spectrum. We are able to use this spectrum to extract not only the first order quadrupole-quadrupole and Van der Waals constants but also sensitive atom-atom interaction parameters such as the spin-spin, spin-orbit, and perturbative constants which arise from interactions between different zeroth order molecular states. This technique also allows information to be obtained about near dissociation collisions. The near dissociation regime is difficult to probe using other techniques.
INFORMAL SEMINAR
Monday, April 10, 2000
4:00 PM
Physics Building, Room 204

## "Entanglement Experiments with Trapped Ions"

Dr. David J. Wineland , NIST
[Host: Thomas Gallagher]
SPECIAL COLLOQUIUM
Monday, April 3, 2000
3:00 PM
Physics Building, Room 204
Note special time.

## "Why Bother with Particle Physics?"

ABSTRACT:
As physicists we should continually ask ourselves what we think the most compelling questions to be resolved are. In particle physics we have the "Standard Model" which explains all confirmed experimental results. So, should we even continue to pursue this line of research? This talk will show that there are very important questions that need to be addressed, that in fact the Standard Model is far from complete. Furthermore these questions must be addressed through experiment. I will argue that a program of Hadron Collider physics (in particular the LHC) has the best chance of moving us past the Standard Model. I will also show examples of the many technological challenges that we face in computing and engineering that make the practice of experimental particle physics truly interdisciplinary.
Atomic
Monday, March 27, 2000
4:00 PM
Physics Building, Room 204

## "Very Slow H+ + D(1s) “Half” Collisions."

Erics Wells , Kansas State
[Host: Robert Jones]
ABSTRACT:
The dissociation of the HD+(1s sigma) molecular ion from the vibrational continuum produces a H+ + D(1s) “half” collision, typically with a with a kinetic energy release upon dissociation of less than 0.5 eV. The vibrational continuum is populated by single ionization of the neutral molecule, which predominantly leads to creation of HD+ molecular ions, but about 1% of the time reaches the vibrational continuum,resulting in a dissociation. Using this natural particle accelerator, we study the charge transfer and elastic scattering in the H+ + D(1s) system at collision energies ( 0 =< Ek =< 1100 meV) much lower than have previously been obtained. Our experimental results for both channels are compared to our coupled channels calculations. Additionally, the sum of the elastic and charge transfer channels relative to the HD+ channel is also compared to the expected ratio of bound-free to total transitions within the Franck-Condon approximation.
SPECIAL COLLOQUIUM
Monday, March 20, 2000
3:00 PM
Physics Building, Room 204
Note special time.

## "Neutrino, Elementary Particle and SuperSTAR"

Nickolas Solomey , Enrico Fermi Institute - University of Chicago
ABSTRACT:
Today there is much concern about the tiny neutral particle the neutrino. It has been in the lime-light in the popular press from science magazines to headlines in the New York Times. This is a great change from when the particle was first postulated to exist. Even its advocates doubted its existence at that point. However, now, the neutrino plays a pivotal role in many major discoveries in elementary particle physics, astrophysics and cosmology, and will continue to be important to study for decades to come. This colloquium will describe the neutrino, discuss its major role in advancing our understanding of elementary particle physics and conclude with the exciting new results we can expect from future experiments currently under construction.
SPECIAL COLLOQUIUM
Monday, March 6, 2000
3:00 PM
Physics Building, Room 204
Note special time.

## "CP Violation at BaBar -- current status and future prospects"

Ted Liu , Lawrence Berkeley Laboratory
ABSTRACT:
In this talk I first present a brief overview of mixing and CP violation in the charm and beauty sectors. Then, I will present a status report from the BaBar experiment at the Stanford Linear Accelerator Center which has been designed especially to measure time-dependent asymmetries in the B meson decays whose interpretation in the Standard Model is directly related to the parameters of the Cabibbo-Kobayashi-Maskawa mixing matrix. At the end, I will comment on the future prospects.
SPECIAL COLLOQUIUM
Monday, February 28, 2000
3:00 PM
Physics Building, Room 204
Note special time.

## "Studying CP Violation at the SLAC B- Factory"

Carlo Dallapicolla , University of Maryland
ABSTRACT:
One of the least-well tested areas of particle physics today is that of CP violation. Although it has been observed in certain particle decays, its origin and magnitude is not well understood. CP violation in particle interactions is a crucial ingredient in the Big Bang model's description of the predominance of matter over antimatter in the universe. A new physics program at the "B-Factory" at the Stanford Linear Accelerator is underway and promises to resolve this important issue.
Atomic
Monday, February 28, 2000
4:00 PM
Physics Building, Room 204

## "Optics With Cold Atoms and Bose Condensates"

Malcolm Boshier , Centre for Optical and Atomic Physics - University of Sussex
[Host: Bloomfield]
Special High Energy Seminar
Monday, February 21, 2000
3:00 PM
Physics Building, Room 204
Note special time.

## "Tevatron QCD and Beyond"

Robert Hirosky , University of Ilinois, Chicago
ABSTRACT:
The D-Zero Experiment studies the world's most energetic hadron collisions at the Fermilab Tevatron accelerator. The study of such collisions provides our deepest glimpse into the structure of matter. Particularly hard scattering of hadron constituents may be evidenced by the production of hadronic jets' or plumes of particles. I review several analyses of jet production from the recent collider run at the Tevatron and survey various physics objectives for Run II' and beyond.
Special Colloquium/Atomic Seminar
Monday, February 21, 2000
4:00 PM
Physics Building, Room 204

## "Entanglement of Four Particles"

Cass Sackett , NIST
[Host: Louis Bloomfield]
ABSTRACT:
Quantum mechanics allows for many-particle wave functions that cannot be factorized into a product of single-particle wave functions, even when the constituent particles are entirely distinct. Such entangled states explicitly demonstrate the nonlocal character of quantum theory, have been suggested for use in high-precision spectroscopy, and are a fundamental element of schemes for quantum communication, cryptography, and computation. In general, the more particles which can be entangled, the more clearly nonclassical effects are exhibited and the more useful the states are for quantum applications. In pursuit of these goals, we have demonstrated a recently proposed entanglement technique applicable to trapped ions. Coupling between the ions is provided by the Coulomb interaction through their collective motional degrees of freedom, but actual motional excitation is minimized. Entanglement is achieved using a single laser pulse, and the method can in principle be applied to any number of ions. We used this technique to generate entangled states of two, and for the first time, four particles.
Special Colloquium/Atomic Seminar
Monday, February 14, 2000
2:00 PM
Physics Building, Room 203
Note special time.
Note special room.

## "Quantum Noise in Simple Atomic Systems"

Samir Bali , Duke University
[Host: Louis Bloomfield]
ABSTRACT:
Counter-intuitive predictions of quantum mechanics are most readily explored in the field of optics, where table-top experiments suffice to make sensitive measurements. A single atom, radiating in free space, is the simplest and most fundamental quantum optical system. It is particularly attractive for study of multiple measurements on a quantum system because, quite unlike the situation for a classical radiator, the detection of a radiated photon directly affects the probability of a subsequent emission. Indeed, measurement of fluctuations in the radiated intensity provided the first experimental evidence for such counter-intuitive quantum effects as photon antibunching and sub-Poissonian light. However, quantum fluctuations in the optical phase of the radiated light remain relatively unexplored. Especially remarkable is the fact that "squeezing" in single-atom fluorescence, a phase-sensitive quantum effect first predicted in 1981, has long eluded direct observation despite receiving considerable attention. The reason is that measurement of phase-sensitive nonclassical effects in atomic fluorescence presents severe experimental challenges. In this talk I will describe how we recently overcame these challenges to make the first measurements of single-atom squeezing spectra in the phase-dependent fluorescence of atoms radiating in free space. Our experimental scheme permits a valid comparison of the observations with our predictions, thus yielding a new and simple physical picture of phase-dependent quantum noise in atomic fluorescence. Results of a direct measurement of the two-time field correlations will also be presented. Our measurements help elucidate the basic atomic processes underlying "squeezing". Our observations are especially important because the measurement accuracy in current state-of-the-art cold atom interferometers and frequency standards is limited by quantum noise. Controlling the phase-dependent quantum noise may enable measurement beyond quantum limits.
Atomic
Monday, January 24, 2000
4:00 PM
Physics Building, Room 204

## "From Laser-cooled Atoms to an Ultra cold Neutral Plasma"

Tom Killian , NIST
[Host: Tom Gallagher]
Atomic
Monday, January 17, 2000
4:00 PM
Physics Building, Room 204

## "The Quest for Quantum Degeneracy in an Optically Trapped Gas of Fermions"

Dr. Smair Bali , Duke University
[Host: Olivier Pfister]
ABSTRACT:
A quantum degenerate sample of cold dilute fermions is expected to yield new exciting physics since Pauli's exclusion principle forbids congregation of fermions in the same quantum state. A fascinating possibility is the formation of Cooper pairs, analogous to the BCS phase transition responsible for superconductivity and for superfluidity in liquid He-3. Lithium-6, a stable and naturally abundant fermionic isotope, is an excellent candidate because it has large and attractive interatomic interactions, a necessary requirement for the superfluid transition. However, the lowest lying spin states of lithium-6 are not magnetically trappable. This precludes the use of a magnetic trap, the only kind of trap in which BEC has been achieved for bosonic atoms. The possibility of achieving quantum degeneracy, whether boson or fermion, in an optical trap has been a long sought goal and is of intense current interest. This is because, unlike their magnetic counterparts, optical traps can trap all spin states and offer the possibility of arbitrary control of interatomic interactions via external magnetic fields. However, owing to the presence of unexplained heating rates, optical traps have failed to be stable. We have identified some of the important heating mechanisms. By minimizing their effect we have constructed an ultrastable optical trap consisting of a focused far-detuned CO2 laser beam, in which we confine lithium-6 atoms with a life-time of 300 secs. This is nearly a two order of magnitude improvement in stability over all previous optical traps, rivalling that of magnetic traps. We simultaneously confine the two lowest lying spin states of lithium-6 thus enabling efficient evaporative cooling toward Fermi degeneracy and, possibly, the superfluid transition. Measurements of anomalously large elastic collision cross-sections and observation of evaporative cooling of lithium-6 will be presented.
Atomic
Monday, December 13, 1999
4:00 PM
Physics Building, Room 204

## "Decoherence of Quantum Superpositions Coupled to Engineered Reservoirs"

Cass Sackett , NIST
[Host: T. Gallagher]
ABSTRACT:
The theory of quantum mechanics applies to closed systems. In such ideal situations, a single atom can exist, for example, in a superposition of being in two different positions at the same time. Real systems, in contrast, always interact with their environment, with the consequence that macroscopic quantum superpositions like Schrodinger's cat are not observed. Moreover, macroscopic superpositions decay so quickly that the dynamics of decoherence can not even be observed. However, mesoscopic systems offer the possibility of observing the decoherence of such quantum superpositions states of the motion of a single trapped atoms. Decoherence is induced by coupling the atoms to engineered reservoirs, where the coupling an state of the environment are under the experimenter's control. We exhibit this with three experiments, finding that the decoherence scales exponentially with the square of the size of the superposition.
Atomic
Monday, December 6, 1999
4:00 PM
Physics Building, Room 204

## "Ultra-Slow Light"

Dr. Mikhail Lukin , ITAMP/Harvard University
[Host: Olivier Pfister]
SPECIAL ATOMIC SEMINAR
Tuesday, November 30, 1999
4:00 PM
Physics Building, Room 204
Note special date.

## "Polarized Entangled Photons In Quantum Communications and Optical Metrology"

Prof. Alexander Sergienko , Boston University
[Host: Olivier Pfister]
ABSTRACT:
A pair of photons (two-photon state) generated in the nonlinear process of type-II spontaneous parametric down conversion (SPDC) is strongly entangled in energy, polarization, time, and space (momentum). Although these two-photon entangled states have primarily been used in fascinating tests of some of the counterintuitive foundations of the quantum theory, their quantum features are also a powerful generator of novel practical applications which either outperform their classical counterparts or do not have any classical analogues at all. We shall discuss a several experimental results in the area of quantum communications and optical measurement.
Special Atomic Seminar
Monday, November 22, 1999
2:00 PM
Physics Building, Room 313
Note special time.
Note special room.

## "Diode Lasers for Atom Traps"

Professor George Ruff , Bates College
[Host: Olivier Pfister]
Atomic
Monday, November 22, 1999
4:00 PM
Physics Building, Room 204

## "New phenomena from solvable models of quantum dynamics "

Timothy Newman , University of Virginia
[Host: Olivier Pfister]
ABSTRACT:
The rich behavior of the dynamics of quantum systems is still being uncovered, both through theoretical and experimental research. In this talk I will discuss some recent work on simple quantum dynamical models, where exact predictions are possible. Despite their simplicity, these models exhibit curious phenomena, including quantum revivals, quantum carpets, and "the sound of one hand clapping". I will also attempt to answer the contemporary question "why not just solve these models on the computer?"
Atomic
Monday, November 1, 1999
4:00 PM
Physics Building, Room 204

## "Optical Tools for Bose-Einstein Condensates"

Dr. Chandra Raman , M.I.T.
[Host: Bob Jones]
Atomic
Monday, October 25, 1999
4:00 PM
Physics Building, Room 204

## "Handedness in the Universe: Chirality in Chemisty"

Dr. Robert Compton , University of Tennessee
[Host: Jan Harrison]
Atomic
Monday, September 20, 1999
4:00 PM
Physics Building, Room 204