Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session C04: Dissipation and Non-Equilibrium DynamicsInvited Live
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Chair: Kadden Hazzard, Rice University |
Tuesday, June 1, 2021 10:30AM - 11:00AM Live |
C04.00001: Quantum many-body scars and weak ergodicity breaking: from Rydberg atoms to the tilted Fermi-Hubbard model Invited Speaker: Zlatko Papic Recent experiments on large chains of Rydberg atoms have found surprising signatures of non-ergodic dynamics, such as robust periodic revivals in global quenches from certain initial states. This weak form of ergodicity breaking has been dubbed "quantum many-body scars" by analogy with unstable classical periodic orbits of a single particle confined to a stadium billiard. In this talk, I will argue that this analogy can be further strengthened by formulating a mean-field type approximation for the atoms residing on even and odd sublattices of the chain.This approach not only provides accurate approximations of scarred eigenstates of this non-integrable system, but it also has a direct relation with the system's semiclassical dynamics. In the second part of the talk, I will present a proposal for an experimental realisation of quantum many-body scars using cold atoms in an optical lattice, describing a 1D Fermi-Hubbard model with a magnetic field gradient. This new platform allows to probe the interplay of scars with other forms of ergodicity breaking, such as Stark many-body localisation and Hilbert space fragmentation due to a dipole moment symmetry. |
Tuesday, June 1, 2021 11:00AM - 11:30AM Live |
C04.00002: Highly out-of-equilibrium 1D gases: experiments and generalized hydrodynamics Invited Speaker: David S. S Weiss Non-equilibrium dynamics in nearly integrable systems, long a theoretical challenge in most regimes, can now be calculated using generalized hydrodynamics (GHD). GHD depends on the continuum approximation and the assumption that the generalized Gibbs ensemble is always locally satisfied. We have tested GHD using ensembles of 1D Bose gases, challenging its two central assumptions in experiments with as few as a dozen particles per gas and using very strong trap quenches, after which the density increases by as much as 35 times. We find excellent theory-experiment agreement for a range of dimensionless coupling strengths and for long times. We follow these dynamics by directly measuring the evolving distribution of rapidities (the momenta of the systems quasiparticles). By also measuring evolving momentum distributions, we can effectively observe how the nature of the quasiparticles themselves change. |
Tuesday, June 1, 2021 11:30AM - 12:00PM Live |
C04.00003: Non-unitary Dynamics via Spacetime Duality Invited Speaker: Vedika Khemani The addition of non-unitary ingredients to many-body quantum dynamics has led to a series of exciting developments in recent years, including new out-of-equilibrium entanglement phases and phase transitions enabled by quantum measurements. I will present recent work [1] in which we show that a duality transformation between space and time on one hand, and unitarity and non-unitarity on the other, can be used to realize non-unitary evolutions whose steady states exhibit a rich variety of behavior in the scaling of their entanglement with subsystem size — from logarithmic to extensive to fractal. These outcomes are closely related to the question of entanglement growth in time under different kinds of unitary dynamics, from localized to chaotic. This connection is sharpened by an exact mapping to unitary evolution with edge decoherence, in which information is irreversibly "radiated away" from one edge of the system. Finally, I will discuss how these ideas could be experimentally realized with present-day or near-term quantum technologies, and how spacetime duality allows us to mitigate (or eliminate altogether) the overhead from "postselection" of random measurement outcomes [2]. [1] Matteo Ippoliti, Tibor Rakovszky, Vedika Khemani, arxiv:2103.06873 [2] Matteo Ippoliti, Vedika Khemani, PRL 126, 060501 (2021) |
Tuesday, June 1, 2021 12:00PM - 12:30PM Live |
C04.00004: Universality in non equilibrium dynamics Invited Speaker: Joerg Schmiedmayer We study strong cooling quench and demonstrate universal scaling of dynamics of the induced non-equilibrium dynamics in time and space. The time evolution within the scaling period is described by a single universal function and scaling exponent, independent of the species of the initial state which constitutes a crucial step in the verification of universality far from equilibrium [1]. Out experiment suggest that the dynamics is governed by a non-equilibrium generalization of Renormalization and can be described by the approach of a non-thermal fixed point. This suggests a comprehensive classification of systems far from equilibrium based on their universal properties similar to the universality classes in phase transitions. Similarly, this can be the basis for a new type of quantum simulation that let us explore a large variety of systems at different scales. |
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