Bulletin of the American Physical Society
48th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 62, Number 8
Monday–Friday, June 5–9, 2017; Sacramento, California
Session N2: Focus Session: Many-body localizationFocus
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Chair: Benjamin Lev, Stanford University Room: 306-307 |
Thursday, June 8, 2017 10:30AM - 11:00AM |
N2.00001: Quantum Stat Mech in a Programmable Spin Chain of Trapped Ions Invited Speaker: Christopher Monroe Trapped atomic ions are a versatile and very clean platform for the quantum programming of interacting spin models and the study of quantum nonequilibrium phenomena. When spin-dependent optical dipole forces are applied to a collection of trapped ions, an effective long-range quantum magnetic interaction arises, with reconfigurable and tunable graphs. Following earlier work on many-body spectroscopy\footnote{C. Senko, et al., \textbf{Science 345}, 430 (2014).} and quench dynamics\footnote{P. Richerme, et al., \textbf{Nature 511}, 198 (2014).}, we have recently studied many body non-thermalization processes in this system. Frustrated Hamiltonian dynamics can lead to prethermalization\footnote{B. Neyenhuis, et al., \textbf{arXiv 1608.00681} (2016).}, and by adding programmable disorder between the sites, we have observed the phenomenon of many body localization (MBL)\footnote{J. Smith, et al., \textbf{Nature Physics 12}, 907 (2016).}. Finally, by applying a periodically driven Floquet Hamiltonian tempered by MBL, we report the observation of a discrete ``time crystal” in the stable appearance of a subharmonic response of the system to the periodic drive\footnote{J. Zhang, et al., \textbf{arXiv 1609.08684} (2016).} [Preview Abstract] |
Thursday, June 8, 2017 11:00AM - 11:30AM |
N2.00002: Exploring many-body localization in two dimensions Invited Speaker: Christian Gross The question of thermalization in closed quantum systems is currently a topic of intense research and ultracold atoms are an ideal experimental system for its study. In this context it is particularly interesting to study systems that do not thermalize. Many-body localized systems form a generic class of such systems, which is largely unexplored in higher dimensions and at high energy densities. Here we report on experiments with single site resolved ultracold lattice bosons in two dimensions subject to random disorder. Our data indicates a transition from thermalizing behavior at low disorder to localization at higher disorder and a diverging length scale at the transition. We also discuss recent experimental progress on the local characterization of disordered lattice bosons at low energy density. [Preview Abstract] |
Thursday, June 8, 2017 11:30AM - 11:42AM |
N2.00003: Progress towards measurement of entanglement entropy dynamics in one-dimensional interacting systems in the presence of disorder Alexander Lukin, M. Eric Tai, Matthew Rispoli, Robert Schittko, Tim Menke, Adam Kaufman, Markus Greiner Many-body localized states appear at odds with thermalization as they preserve the memory of their initial state. This behavior has drawn significant theoretical and experimental attention in recent years. Real space localization has been observed on various platforms and under a number of experimental conditions, both with and without interactions. However, the characteristic logarithmic growth of entanglement entropy, which distinguishes the many-body localized state from the non-interacting Anderson localized state, has only been studied in numerics and has yet to be investigated experimentally. We are working towards the phenomenon of localization in one dimensional, interacting Bose-Hubbard system using a quantum gas microscope. With site-resolved addressing and readout, our microscope provides full control over the studied system, in particular it allows us to add disorder into our system using a Fourier plane hologram. This gives us access to both local observables, such as the occupation of individual lattice sites, as well as the entanglement entropy. I will present our progress towards measuring the dependence of the entanglement entropy grows on the disorder strength and interactions in our system. [Preview Abstract] |
Thursday, June 8, 2017 11:42AM - 11:54AM |
N2.00004: Probing many-body localization with semi-classical phase-space methods} Oscar L. Acevedo, Arghavan Safavi-Naini, Johannes Schachenmayer, Rahul Nandkishore, Ana Maria Rey The Discrete Truncated Wigner Approximation (DTWA) has been proven to successfully predict several aspects of many-body quantum dynamics. This approach is based on an exact phase-space representation of the initial state of a discrete quantum system, and estimates the time evolution by classical mean field equations. In this work, we show that these methods are suitable for exploring Many-Body Localization (MBL) in disordered and interacting spin 1/2 arrays. By taking as benchmark case a 1D Heisenberg model, we show that DTWA is able to reproduce dynamical signatures of the MBL phase such as long-time persistence of initial state information and logarithmic growth of entanglement, even though a pure mean field analysis would lead to no dynamics at all. Our approximate results are able to characterize the thermal phase and many aspects of the MBL phase, especially in the large disorder limit. Our observations indicate potential exciting opportunities for the use of phase-space methods to study MBL in regimes where efficient exact solutions are not available, such as systems with long range interactions in higher dimensions. Those systems are in the reach of current cold atom experiments. [Preview Abstract] |
Thursday, June 8, 2017 11:54AM - 12:06PM |
N2.00005: Exploring localization and out-of-time ordered correlations in nuclear spin chains Xuan Wei, Chandrasekhar Ramanathan, Paola Cappellaro Measuring the spread of information is a complex but central task for characterizing out-of-equilibrium many-body dynamics. We present a novel correlation metric capable of detecting information spread in a many-spin system at high temperature. We experimentally demonstrate the use of this metric to probe information scrambling in a solid-state spin system using nuclear magnetic resonance (NMR). We observe a slow growth of correlations consistent with the phenomenology of many-body localization (MBL). In addition, we experimentally measure in our system the commutator square, akin to out-of-order correlations, and observe a similar slow growth in the MBL regime. Furthermore, we observe a fast growth of the commutator square near a critical point corresponding to a symmetry breaking phase transition. [Preview Abstract] |
Thursday, June 8, 2017 12:06PM - 12:18PM |
N2.00006: Partial breakdown of quantum thermalization in a Hubbard-like model James R. Garrison, Ryan V. Mishmash, Matthew P. A. Fisher We study the possible breakdown of quantum thermalization in a model of itinerant electrons on a one-dimensional chain without disorder, with both spin and charge degrees of freedom. The eigenstates of this model exhibit peculiar properties in the entanglement entropy, the apparent scaling of which is modified from a ``volume law'' to an ``area law'' after performing a partial, site-wise measurement on the system. These properties and others suggest that this model realizes a new, non-thermal phase of matter, known as a quantum disentangled liquid (QDL). The putative existence of this phase has striking implications for the foundations of quantum statistical mechanics. [Preview Abstract] |
Thursday, June 8, 2017 12:18PM - 12:30PM |
N2.00007: Thermalization in a Disordered Boson Lattice Gas Laura Wadleigh, Philip Russ, Brian DeMarco The process of thermalization in closed, strongly interacting, disordered quantum systems is not well understood. We have developed a new technique to study this problem using ultracold 87Rb atoms trapped in a disordered cubic optical lattice. We cool the gas in the presence of a cylindrical optical barrier, which creates a hole in the atomic density profile. The barrier is suddenly removed and in situ images are taken over four orders of magnitude in tunneling time as the gas is allowed to thermalize. We use a multivariate statistical analysis applied to images to detect deviations from thermal equilibrium. We will discuss the timescale for equilibration in the superfluid, Mott insulator, and many-body localized regimes. [Preview Abstract] |
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