Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session S27: Non-Equilibrium Physics with Cold Atoms and Molecules, Rydberg Gases, and Trapped Ions IILive
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Sponsoring Units: DAMOP DCMP Chair: Hannes Bernien, University of Chicago |
Thursday, March 18, 2021 11:30AM - 11:42AM Live |
S27.00001: Anomalous Diffusion in Dipole- and Higher-Moment Conserving Systems Johannes Feldmeier, Pablo Sala de Torres-Solanot, Giuseppe De Tomasi, Frank Pollmann, Michael Knap The presence of global conserved quantities in interacting systems generically leads to diffusive transport at late times. Here, we show that systems conserving the dipole moment of an associated global charge, or even higher moment generalizations thereof, escape this scenario, displaying subdiffusive decay instead. Modelling the time evolution as cellular automata for specific cases of dipole- and quadrupole-conservation, we numerically find distinct anomalous exponents of the late time relaxation. We explain these findings by analytically constructing a general hydrodynamic model that results in a series of exponents depending on the number of conserved moments, yielding an accurate description of the scaling form of charge correlation functions. We analyze the spatial profile of the correlations and discuss potential experimentally relevant signatures of higher moment conservation. |
Thursday, March 18, 2021 11:42AM - 11:54AM Live |
S27.00002: Scattering of mesons in quantum simulators Federica Maria Surace, Alessio Lerose Simulating real-time evolution in theories of fundamental interactions represents one of the central challenges in contemporary theoretical physics, due to the failure of conventional analytical techniques and numerical simulations. Cold-atom platforms represent promising candidates to realize quantum simulations of non-perturbative phenomena in gauge theories, such as vacuum decay and hadron collisions, in extreme conditions prohibitive for direct experiments. In our work, we demonstrate that present-day quantum simulators can give access to S-matrix measurements of elastic and inelastic meson collisions in Abelian gauge theories, mimicking experiments with linear particle accelerators. Considering for definiteness a (1 + 1)-dimensional Z2-lattice gauge theory realizable with Rydberg-atom arrays, we solve the meson scattering problem exactly in the limit of large fermion mass and for arbitrary coupling strength. |
Thursday, March 18, 2021 11:54AM - 12:06PM Live |
S27.00003: Spin squeezing dynamical phase transition in the power-law XXZ model Michael A. Perlin, Chunlei Qu, Ana Maria Rey We investigate spin squeezing dynamics in an XXZ model with interactions that fall off with distance r as 1/rα in D=2 and 3 spatial dimensions. In stark contrast to the Ising model, we find a broad parameter regime where spin squeezing comparable to the infinite-range (α=0) limit is achievable even when interactions are short-ranged (α>D). A region of "collective" behavior in which optimal squeezing grows with system size extends all the way to the infinite-α limit of nearest-neighbor interactions. We identify this region with a dynamical phase of the power-law XXZ model, and discuss connections to thermal equilibrium and ground-state phases. Our predictions, made using the discrete truncated Wigner approximation, are testable in a variety of experimental cold atomic, molecular, and optical platforms. |
Thursday, March 18, 2021 12:06PM - 12:18PM Live |
S27.00004: Subharmonic stabilization of quantum many-body scars in Rydberg atom arrays Dolev Bluvstein, Ahmed Omran, Harry Levine, Alexander Keesling, Giulia Semeghini, Sepehr Ebadi, Tout T Wang, Alexios Michailidis, Nishad Maskara, Wen Wei Ho, Maksym Serbyn, Markus Greiner, Vladan Vuletic, Mikhail Lukin Understanding and controlling quantum entanglement dynamics in many-body systems away from equilibrium is an outstanding challenge. In complex systems, such dynamics typically leads to chaotic spreading throughout the Hilbert space associated with thermalization. Using a programmable quantum simulator based on Rydberg atom arrays in one and two dimensions, we experimentally investigate dynamics resulting from rapid quenches across quantum phase transitions. For specific initial states on a wide variety of bipartite lattices, we observe collapses and revivals of the order parameters, corresponding to quantum many-body scars, and explore their thermalization mechanisms. Remarkably, we discover that scar revivals can be stabilized by applying a periodic drive, which further locks the scar oscillation frequency to half the drive frequency. We map phase diagrams of this subharmonic response and show its robustness increases with system size, akin to time crystalline behavior. These observations challenge understandings of quantum thermalization and allow for steering entanglement growth in many-body systems. I will also showcase other recent efforts on quantum simulation of 2D phases and quantum optimization. |
Thursday, March 18, 2021 12:18PM - 12:30PM Live |
S27.00005: Observation of a Dynamical Phase Transition in a Quantum Simulator of Lipkin-Meshkov-Glick Model using Bosonic Gases Anjun Chu, Johannes Will, Jan Arlt, Carsten Klempt, Ana Maria Rey We theoretically propose and experimentally demonstrate the use of motional sidebands in a trapped thermal ensemble of 87Rb atoms to engineer tunable long-range XXZ spin models. We benchmark our simulator by probing a ferromagnetic to paramagnetic dynamical phase transition in the Lipkin-Meshkov-Glick (LMG) model, a collective XXZ model plus additional transverse and longitudinal fields, via Rabi spectroscopy. We experimentally reconstruct the boundary between the dynamical phases, which is in good agreement with mean-field theoretical predictions. Our work introduces new possibilities in quantum simulation of anisotropic spin-spin interactions and quantum metrology enhanced by many-body entanglement. |
Thursday, March 18, 2021 12:30PM - 12:42PM Live |
S27.00006: Non-equilibrium dynamics of a 2D Bose gas near a critical point Shinichi Sunami, David Garrick, Abel Beregi, Adam J Barker, Kathrin Luksch, Elliot Bentine, Christopher J Foot We report experimental measurements of the relaxation dynamics of 2D Bose gases following the coherent splitting into two 2D clouds. The splitting of low-dimensional ultracold gases produces a non-equilibrium initial state with spatially uniform relative phase; the transformation from a single- to a double-well potential is implemented by applying RF radiation at multiple frequencies to form dressed states of Rb-87 atoms in a magnetic quadrupole field and by dynamically modulating the RF amplitudes [1]. The relative phase of the two clouds is detected by imaging the cross-section of matter-wave interference after Time-of-Flight expansion [1]. |
Thursday, March 18, 2021 12:42PM - 12:54PM Live |
S27.00007: Many-Body Dephasing in Long-range Transverse-field Ising Chain with Trapped Ions Lingzhen Guo, Harvey B Kaplan, Wen Lin Tan, Arinjoy De, Florian Marquardt, Guido Pagano, Christopher Monroe We investigate how a closed interacting quantum many-body system dephases as a function of time. We analyse the persistent temporal fluctuations after a quantum quench of a tunable long-range interacting transverse-field Ising Hamiltonian, which is realized with a trapped-ion quantum simulator. The one dimensional transvese-filed Ising chain has long-range power-law interactions. In the small coupling exponent regime, the properties of the system are closely related to the integrable Hamiltonian with global spin-spin coupling. Based on the eigenstate thermalization hyperthesis (ETH), we develop a non-perturbative method to get the analytical expresssion for the temopral fluctuations. The analytical expression for the temporal fluctuations predicts the exponential suppression of temporal fluctuations with increasing system size, which is consistent with our measurement data. |
Thursday, March 18, 2021 12:54PM - 1:06PM Live |
S27.00008: Hypergrid subgraphs and the origin of many-body scars in constrained quantum systems Jean-Yves Desaules, Kieran Bull, Christopher Turner, Zlatko Papic Following the recent experimental observation of wave function revivals in chains of interacting Rydberg atoms, much effort has focused on understanding the origin of many-body scars in non-integrable quantum systems. Here we argue that the many-body wave function revivals in these models stem from large hypergrid subgraphs within the adjacency graph corresponding to the quantum Hamiltonian. We explicitly identify such substructures in several constrained spin models known to host quantum many-body scars. The appearance of embedded hypergrid graphs is physically enabled by the Hilbert space constraints, and they constitute a minimal structure for an emergent su(2) spectrum-generating algebra which gives rise to quantum revivals. We illustrate our approach by providing a graph-theoretic interpretation of the Rydberg atom model, and by constructing new many-body scarred models which support robust quantum revivals from experimentally-preparable initial states. |
Thursday, March 18, 2021 1:06PM - 1:18PM Live |
S27.00009: Emergent symmetries and slow quantum dynamics in a Rydberg chain with confinement I Chi Chen, Thomas Iadecola Rydberg atoms in optical tweezer arrays provide a playground for nonequilibrium quantum many-body physics. The PXP model describes the dynamics of such systems in the strongly interacting Rydberg blockade regime and notably exhibits weakly nonergodic dynamics due to quantum many-body scars. Here, we study the PXP model in a strong staggered external field, which has been proposed to manifest quasiparticle confinement in light of a mapping to a lattice gauge theory. We characterize this confining regime using both numerical exact diagonalization and perturbation theory around the strong-field limit. In addition to the expected emergent symmetry generated by the staggered field, we find a second emergent symmetry that is special to the PXP model. The interplay between these emergent symmetries and the Rydberg blockade constraint dramatically slows down the system's quench dynamics beyond what is found in other systems with confinement. We devise a nested Schrieffer-Wolff perturbation theory to derive the effective Hamiltonian with both emergent symmetries and show that this treatment is essential to understand the numerically observed relaxation timescales under quantum quenches from initial product states. |
Thursday, March 18, 2021 1:18PM - 1:30PM Live |
S27.00010: Time crystal in a static cavity QED Hamiltonian Saeed Rahmanian Koshkaki, Michael Kolodrubetz In this work, we study how localization in the presence of a long-range coupling can hosts new symmetry breaking and topological phases with non-trivial correlations. The long-range coupling can be mediated by photons in cavity QED or other global modes, such as a central spin-$S$. One of the interesting emergent phases is a time crystal, which exists in thermal equilibrium for this cavity QED Hamiltonian. We investigate the stability of time crystal to dissipation, which naturally occurs in real experimental systems. We also discuss analytical methods to determine stability, including a high-frequency expansion that allows adiabatic elimination of the photon degree of freedom. |
Thursday, March 18, 2021 1:30PM - 1:42PM Live |
S27.00011: Nonadiabatic Phase Transition with Broken Chiral Symmetry Nikolai Sinitsyn, Bin Yan, Vladimir Y Chernyak, Wojciech Hubert Zurek We explore nonadiabatic quantum phase transitions in an Ising spin chain with a linearly time-dependent transverse field and two different spins per unit cell. Such a spin system passes through critical points with gapless excitations, which support nonadiabatic transitions. Nevertheless, we find that the excitations on one of the chain sub-lattices are suppressed in the nearly-adiabatic regime exponentially. Thus, we reveal a coherent mechanism to induce exponentially large density separation for different quasiparticles. |
Thursday, March 18, 2021 1:42PM - 1:54PM Live |
S27.00012: Localization and criticality in antiblockaded 2D Rydberg atom arrays Fangli Liu, Zhicheng Yang, Przemyslaw Bienias, Thomas Iadecola, Alexey V Gorshkov Controllable Rydberg atom arrays have provided new insights into fundamental properties of quantum matter both in and out of equilibrium. We study the effect of positional disorder on Rydberg atoms trapped in a 2D square lattice under anti-blockade conditions. We show that this condition leads to the connectivity of a particular subspace of the full Hilbert space to form a 2D Lieb lattice, which features a singular flat band. We consider positional disorder that is naturally present in realistic Rydberg atom arrays. Remarkably, we find three distinct regimes in the phase diagram as the disorder strength is varied: a critical phase, a delocalized but nonergodic phase, and a phase with a disorder-induced flat band. The critical phase's existence depends crucially upon the singular flat band in our model, and is absent in any 1D system. We propose to use quench dynamics to probe the three different regimes experimentally. |
Thursday, March 18, 2021 1:54PM - 2:30PM Live |
S27.00013: George E. Valley, Jr. Prize Invited Speaker: Norman Yao George E. Valley, Jr. Prize |
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