Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session H03: Focus Session: Nonequilibrium Physics |
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Chair: Markus Greiner, Harvard University Room: Grand B |
Wednesday, May 30, 2018 8:00AM - 8:30AM |
H03.00001: Dynamics of a Bose gas quenched to unitarity Invited Speaker: Robert Smith I will give an overview of our recent work on the dynamics of homogeneous Bose gases quenched to unitarity (where the inter-particle interaction strength is as strong as allowed by quantum mechanics). Our work includes studies of atom loss, molecular correlation and momentum distribution dynamics. I will discuss the universal scaling laws that describe the behavior we observe and what they reveal about the unitary Bose gas. [Preview Abstract] |
Wednesday, May 30, 2018 8:30AM - 9:00AM |
H03.00002: Quantum many-body scars: a new form of ergodicity breaking in a Rydberg-atom quantum simulator Invited Speaker: Dmitry Abanin The thermodynamic description of many-particle systems rests on the assumption of ergodicity, the ability of a system to explore all allowed configurations in the phase space. Recent studies of many-body localization have revealed the existence of systems that strongly violate ergodicity in the presence of quenched disorder. Here, we demonstrate that ergodicity can be weakly broken by a different mechanism, arising from the presence of special eigenstates in the many-body spectrum that are reminiscent of quantum scars in chaotic non-interacting systems. In the single-particle case, quantum scars correspond to wave functions that concentrate in the vicinity of unstable periodic classical trajectories. We show that many-body scars appear in the Fibonacci chain, a model with a constrained local Hilbert space that has been recently experimentally realized in a Rydberg-atom quantum simulator. The quantum scarred eigenstates are embedded throughout the otherwise ergodic many-body spectrum, but lead to direct experimental signatures, as we show for periodic recurrences that reproduce those observed in the experiment. Our results suggest that scarred many-body bands give rise to a new universality class of quantum dynamics, opening up opportunities for the creation of novel states with long-lived coherence in systems that are now experimentally realizable. [Preview Abstract] |
Wednesday, May 30, 2018 9:00AM - 9:12AM |
H03.00003: Probing the thermal to many-body localized transition in one dimension with single site resolution Alexander Lukin, Matthew Rispoli, Robert Schittko, Sooshin Kim, M. Eric Tai, Vedika Khemani, Adam Kaufman, Julian Leonard, Markus Greiner Many-body localization is an example of the breakdown of quantum thermalization, which occurs in quantum ergodic systems when sufficiently strong disorder is applied. Characteristic features, such as the persistence of the initial state, have been experimentally observed on various platforms, but the growth of non-local correlations has yet to be studied. Here, we probe the interplay of thermalization and localization using a quantum gas microscope, giving us access to site-resolved full counting statistics over multiple decades of time evolution in an isolated system. This allows us to observe correlations that build up both in space and time across the phase transition. We study the decay of density-density correlations as the system crosses into the many-body localized regime and find that the correlation length increases as we approach the critical point. We also observe sub-diffusive temporal dynamics in the particle number fluctuations of subsystems. [Preview Abstract] |
Wednesday, May 30, 2018 9:12AM - 9:24AM |
H03.00004: Critical phenomena of a multicritical point in a driven-dissipative many-body system Jeremy T. Young, Michael Foss-Feig, Alexey V. Gorshkov, Mohammad F. Maghrebi We study a non-equilibrium driven-dissipative bosonic model with hopping and density-density interactions, which contains multicritical points where two real fields become gapless and could be realized experimentally via Rydberg atoms in an optical lattice or a non-linearly coupled cavity array. On the level of mean field theory, these critical points are described by a cusp-Hopf bifurcation, leading to features such as bistability and limit cycles as well as other interesting phases. Beyond mean field theory, we show that these multicritical points can be mapped to a system of two coupled Ising models at different temperatures. Using a perturbative renormalization group approach, we study the critical phenomena of the multicritical point. In particular, we determine whether non-equilibrium behavior persists or if the critical phenomena are described by an equilibrium universality class. [Preview Abstract] |
Wednesday, May 30, 2018 9:24AM - 9:36AM |
H03.00005: The Kibble-Zurek mechanism in a driven dissipative transition Yogesh S Patil, Hil Fung Harry Cheung, Tamiro Villazon, Aditya G Date, Anushya Chandran, Anatoli Polkovnikov, Mukund Vengalattore In open quantum systems, the competition between coherent and dissipative dynamics can give rise to new forms of driven dissipative transitions, dynamical states and critical behavior that lies beyond the standard paradigms of equilibrium phase transitions. We investigate the critical dynamics of a driven dissipative phase transition in the presence of a dynamically engineered non-Markovian environment. We demonstrate that our system exhibits universal scaling behavior following a quench into an ordered phase and confirm the validity of the Kibble-Zurek mechanism in dynamical phase transitions. Further, the growth of the order parameter following such quenches reveals a universal two-parameter scaling function dependent on both the quench rate and the temperature. This two-parameter scaling function thus allows us to access the critical behavior of the zero-temperature transition using finite temperature measurements. We also measure the critical exponents of the phase transition based on the Kibble-Zurek paradigm and show that these exponents are significantly modified due to the non-Markovian system-reservoir interactions. Our studies experimentally confirm the profound effect of environmental correlations on the dynamics of a driven, dissipative transition, and can potentially serve as a touchstone for further experiments on such dynamical transitions in the quantum many-body regime. [Preview Abstract] |
Wednesday, May 30, 2018 9:36AM - 9:48AM |
H03.00006: Many Body Localization without disorder Sayan Choudhury, Qi Zhou Motivated by the question of whether disorder is necessary for many-body localization (MBL), we study the quantum dynamics of a frustrated one-dimensional spin chain without disorder. When the system is prepared at an initial state with one domain wall, a frustration-induced destructive interference suppresses the propagation of excitations. As a result, for a wide parameter regime, this spin chain exhibits many characteristic signatures of MBL including initial state memory retention and the logarithmic growth of entanglement entropy. The lifetime of such quasi-MBL grows exponentially with increasing the size of the system. We further show how an appropriate out-of-time-ordered correlator is correlated to the entanglement entropy. Our findings suggest a new route to access quasi-MBL in a broad class of systems with frustration. [Preview Abstract] |
Wednesday, May 30, 2018 9:48AM - 10:00AM |
H03.00007: Observation of Non-Gaussian Statistics and Levy Flights in Nitrogen Vacancy Centers David Levonian, Michael Goldman, Kristiaan DeGreve, Swati Singh, Daniel Twitchen, Matthew Markham, Mikhail Lukin A nitrogen-vacancy center can be used as a probe of the interacting $^{\mathrm{13}}$C nuclear spins in a diamond crystal. Under the right conditions, its behavior can be described as a random walk with step sizes drawn from a distribution without a well-defined mean or standard deviation. Its behavior is then described by Levy statistics, providing an opportunity to study Levy statistics in a well understood system. [Preview Abstract] |
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