×
Atomic
Monday, May 9, 2022
4:00 PM
Ridley Hall, Room G006

 Add to your calendar

"Quantum and thermal stability of quasiperiodic patterns of ultracold Bose gases"


Tommaso Macri , Universidade Federal do Rio Grande do Norte: Natal, RN, BR
[Host: Peter Schauss]
ABSTRACT:

The search for spontaneous pattern formation in equilibrium phases with genuine quantum properties is a leading direction of current research. We investigate the effect of quantum fluctuations - zero-point motion and exchange interactions - on the phases of an ensemble of bosonic particles with local and nonlocal interactions to determine their ground state properties. In the high-density limit, we observe patterns with 12-fold rotational symmetry compatible with periodic approximants of quasicrystalline phases and their connection to related phases in soft-matter physics. In the second part, I present results for a system of 2D trapped bosons in a quasiperiodic potential at finite temperature. Alongside the superfluid, normal fluid, and insulating phases, we demonstrate the existence of a Bose glass phase, which is robust to thermal fluctuations for a set of parameters within current experiments with quasi-2D optical confinement.

 

References:

[1] B. Abreu, F. Cinti, and T. Macrì, Phys. Rev. B 105, 094505 (2022)

[2] M. Ciardi, T. Macrì, and F. Cinti, Phys. Rev. A 105, L011301 (2022)

[3]  A. Mendoza-Coto, R. Turcati, V. Zampronio, R. Díaz-Méndez, T. Macrì, F. Cinti, Phys. Rev. B 105, 134521 (2022)

[4] N. Defenu, T. Donner, T. Macrì, G. Pagano, S. Ruffo, A. Trombettoni, arXiv:2109.01063 (2021)

Atomic
Monday, April 25, 2022
3:30 PM
Ridley Hall, Room G006
Note special time.

 Add to your calendar

"Phonon-assisted tunneling through a p-n junction in bilayer graphene"


Jianguang Yang , University of Virginia - Department of Physics
[Host: Dima Pesin]
ABSTRACT:

It was shown that elastic tunneling through a p-n junction in gapped bilayer graphene can lead to oscillatory transmission as a function of bandgap [1], where a combination of the semiclassical considerations and numerical calculations were used. In this talk, I will first present how we confirm the numerical results of that work analytically by using the method of steepest descents, where we treat the momentum as time in Schrödinger's equation in momentum space. In the presence of phonons, we then use a similar approach and generalize it to the phonon-assisted tunneling, I will discuss how the presence of phonons, and the associated inelastic processes, can contribute to the transport across the p-n junction in gapped bilayer graphene. Near zero temperature, I will show phonon can enhance the transmission when an electron emits or absorb a phonon and jump from one branch point to another, and the conductance will behave like a step function in terms of voltage where the conductance increases with the square root of voltage firstly and eventually becomes constant.

[1] R. Nandkishore and L. Levitov, Proceedings of the National Academy of Sciences 108, 14021 (2011)

Atomic
Monday, April 18, 2022
4:00 PM
Ridley Hall, Room G006

 Add to your calendar

"Buidling quantum processors and quantum networks atom-by-atom"


Professor Hannes Bernien , The University of Chicago
[Host: Prof. Peter Schauss]
ABSTRACT:

Reconfigurable arrays of neutral atoms are an exciting new platform to study quantum many-body phenomena and quantum information protocols. Their excellent coherence combined with programmable Rydberg interactions have led to intriguing observations such as quantum phase transitions, the discovery of quantum many-body scars, and the recent realization of a topological spin liquid phase.

Here, I will introduce new methods for controlling and measuring atom arrays that open up new directions in quantum state control, quantum feedback and many-body physics. First, I will introduce a dual species atomic array in which the second atomic species can be used to measure and control the primary species. This will lead to the possibility of performing quantum nondemolition measurements and new ways of engineering large, entangled states on these arrays. Furthermore, prospects of studying open systems with engineered environments will be discussed.

An alternative, hybrid approach for engineering interactions and scaling these quantum systems is the coupling of atoms to nanophotonic structures in which photons mediate interactions between atoms. Such a system can function as the building block of a large-scale quantum network. In this context, I will present quantum network node architectures that are capable of long-distance entanglement distribution at telecom wavelengths.

Atomic
Monday, April 11, 2022
4:00 PM
Ridley Hall, Room G006

 Add to your calendar

"Quantum gas microscopy of triangular-lattice Mott insulators"


Liyu Liu , University of Virginia - Department of Physics
[Host: Prof. Peter Schauss]
ABSTRACT:

High temperature superconductivity is of high scientific interest. The underlying physics is captured by the Hubbard model. Based on this model, Anderson's resonating valence bond (RVB)concepts indicate that the strong correlation and frustration are keys to high temperature superconductivity. The triangular lattice Hubbard model is a paradigmatic model of a strongly correlated geometrically frustrated quantum system which exhibits a rich phase diagram including the spin-liquid state predicted by the RVB theory. However, this system is numerically difficult due to the frustration and the large ground state degeneracy. Quantum gas microscopes are at the forefront of quantum simulation, providing a direct site-resolved detection of experimental realizations of the Hubbard model. We realized site-resolved imaging of fermionic Mott Insulators in a novel triangular optical lattice. We measured the spin-spin correlations in these Mott insulators and compared the measured data to Quantum Monte Carlo simulations.

You can also attend virtually via Zoom
 
Zoom Meeting URL:    https://virginia.zoom.us/j/91693752240  Meeting ID: 916 9375 2240      Passcode: 507274

Monday, March 28, 2022
4:00 PM
Hybrid Format, Room Ridley Hall G006 (in-person) | Zoom (online)
Note special room.

 Add to your calendar

"Experimental Improvements for Tune-out Wavelength Spectroscopy with 87Rb"


Elizabeth Larson , University of Virginia - Department of Physics
[Host: Prof. Cass Sackett]
ABSTRACT:

A tune-out wavelength is one at which the dynamical polarizability of an atom is zero; that is, the Stark shifts from higher- and lower-lying states cancel exactly.  Measurements of tune-out wavelengths provide vital experimental access to dipole matrix elements, which are currently the limiting factor in improving theoretical calculations of atomic parity violation.  I will discuss previous measurements of the scalar and vector tune-outs between the 5P excited states of 87Rb, as well as plans to improve measurement precision and complete a first measurement of the 6P tune-outs.

Atomic
Thursday, January 20, 2022
3:30 PM
Physics Building, Room 204
Note special date.
Note special time.
Note special room.

 Add to your calendar

"Spatial symmetry breaking in Kerr-lens mode-locked lasers – beyond the soliton model"


Avi Pe'er , Bar-Ilan University
[Host: Prof. Olivier Pfister]
ABSTRACT:

Kerr-lens mode-locking (KLM) is the work-horse mechanism for generation of ultrashort pulses, where a non-linear lens forms an effective ultrafast saturable absorber within the laser cavity. According to standard theory, the pulse in the cavity is a soliton, with a temporal profile and power determined by the non-linearity to exactly counteract diffraction and dispersion, resulting in pulses, whose power and shape are fixed across a wide range of pump powers. I will present an experimental demonstration and theoretical modeling that a KLM laser in a linear cavity deviates from the soliton model due to the non-local Kerr lens. By breaking the spatial symmetry in the cavity between the forward and backward halves of the round-trip the laser efficiency can surpass the soliton limit in a single pulse, while maintaining stable cavity propagation. We model  the symmetry breaking by numerical simulation and confirm it experimentally in a mode-locked Ti:Sapphire laser with a quantitative agreement to the simulation results. Our numerical tool opens a new window into the crux of mode-locking physics by direct examination of the spatio-temporal dynamics within the Kerr medium, which is difficult (or even impossible) to observe experimentally.

Atomic
Monday, November 29, 2021
4:00 PM
Physics Building, Room 204
Note special room.

 Add to your calendar

"Levitated Optomechanics and the Casimir Effect"


Professor Tongcang Li , Purdue University
[Host: Prof. Peter Schauss]
ABSTRACT:

Optical tweezers provide a non-contact method to manipulate microscopic objects and have many potential applications in precision measurements. Recently, we developed an optically levitated Cavendish torsion balance for quantum-limited torque and force sensing [Phys. Rev. Lett., 121, 033603  (2018)]. We have optically levitated nanoparticles in a vacuum and driven them to rotate up to 300 billion rpm (5 GHz). Using a levitated nanoparticle in a vacuum, we demonstrated ultrasensitive torque detection with a sensitivity several orders higher than the former record [Nature Nanotechnology 15, 89 (2020)]. This system will be promising to study quantum friction, Casimir torque, and gravity at short distances.  We also propose and demonstrate a scheme to achieve strong coupling between multiple micromechanical oscillators with virtual photons, i.e., quantum vacuum fluctuations. Quantum field theory predicts that there are random fluctuations everywhere in a vacuum due to the zero-point energy. The quantum electromagnetic fluctuations can induce a measurable force between neutral objects, which is known as the Casimir effect. We have achieved non-reciprocal energy transfer between two mechanical resonators coupled by quantum vacuum fluctuations [arXiv:2102.12857].

Show More...

To add a speaker, send an email to ps5nw@Virginia.EDU Include the seminar type (e.g. Atomic Physics Seminars), date, name of the speaker, title of talk, and an abstract (if available). [Please send a copy of the email to phys-speakers@Virginia.EDU.]