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 B27: Disorder and Localization in AMO Systems ILive
|
Hide Abstracts |
Sponsoring Units: DAMOP DCMP Chair: Ehud Altman, University of California, Berkeley |
Monday, March 15, 2021 11:30AM - 12:06PM Live |
B27.00001: 2021 Valley Prize Talk: Many-Body Physics in the NISQ Era Invited Speaker: Vedika Khemani This talk will explore the implications of recent breakthough progress in the realm of noisy, intermediate scale quantum (NISQ) devices for quantum many-body physics. We ask which physical phenomena, in the realm of quantum statistical mechanics, can these devices realize better than any other experimental platform. As a target, we identify discrete time crystals (DTCs), novel out-of-equilibrium phases of matter that break time translation symmetry. While precursors of time-crystals have been observed across a variety of experimental platforms - ranging from trapped ions to nitrogen vacancy centers - each of these lacks one or more of the necessary ingredients for realizing a true incarnation of this phase, and detecting the long-range spatiotemporal order that is its defining feature. We show that a new generation of quantum simulators, such as Google's Sycamore processor, can be programmed to realize the DTC phase and to experimentally verify its dynamical properties using a wide range of observables and initial states. We will also present recent results on the study of many-body dynamics in open systems, which is broadly relevant for understanding the effect of environmental decoherence on the observation of novel physics and computational advantage. |
Monday, March 15, 2021 12:06PM - 12:18PM Live |
B27.00002: Characterizing the many-body localization transition through correlations Benjamin Villalonga, Bryan Clark Closed, interacting, quantum systems have the potential to transition to a many-body localized (MBL) phase under the presence of sufficiently strong disorder, hence breaking ergodicity and failing to thermalize. In this work we study the distribution of correlations throughout the ergodic-MBL phase diagram. We find the typical correlations in the MBL phase decay as a stretched exponential with range r eventually crossing over to an exponential decay deep in the MBL phase. At the transition, the stretched exponential goes as exp[−A√r], a decay that is reminiscent of the random singlet phase. While the standard deviation of the log(QMI) has a range dependence, the log(QMI) converges to a range invariant distribution on all other moments (i.e., the skewness and higher) at the transition. The universal nature of these distributions provides distinct phenomenology of the transition different from both the ergodic and MBL phenomenologies. |
Monday, March 15, 2021 12:18PM - 12:30PM Live |
B27.00003: Absence of True Localization in Many-Body Localized Phases Maximilian Kiefer-Emmanouilidis, Razmik Unanyan, Michael Fleischhauer, Jesko Sirker A characteristic feature of many-body localization (MBL) is a logarithmic growth of the von Neumann entanglement entropy S after a quantum quench. In lattice systems with particle-number conservation, S is the sum of number entropy SN and configurational entropy Sconf. Especially, in experiments of ultra cold gases using a quantum gas microscope SN is easily obtained by observing the particle number distribution p(n) of a subsystem. We have recently shown that the logarithmic growth of the entanglement entropy is accompanied by a slow growth of the number entropy, SN∼lnln t[1]. This violates the standard scenario of MBL and raises the question whether the observed behavior is transient or continues to hold at strong disorder in the thermodynamic limit. Here we provide an in-depth numerical study of SN(t) for the disordered Heisenberg chain and find strong evidence that the system is not fully localized even at strong disorder. Calculating the Rényi number entropy SNα(t) for α«1—which is sensitive to large number fluctuations occurring with low probability—we demonstrate that p(n) in one half of the system has a small but continuously growing tail. |
Monday, March 15, 2021 12:30PM - 12:42PM Live |
B27.00004: Construction of Flat band Quantum Scars Yoshihito Kuno, Tomonari Mizoguchi, Yasuhiro Hatsugai We propose a general construction scheme for a quantum scar state in flat band systems. The quantum scar is an atypical eigenstate breaking eigenstate thermalization hypothesis embedded in a many-body energy spectrum. In our construction, we make use of orthogonal compact localized states that are characteristics of certain flat-band models. We concretely discuss our construction scheme, taking a saw-tooth flat lattice system as an example, and numerically demonstrate the presence of a quantum scar state. Furthermore, some examples of higher-dimensional systems are also proposed. Our construction method of quantum scar has broad applications to various flat band systems. |
Monday, March 15, 2021 12:42PM - 12:54PM Live |
B27.00005: Dynamics in centrally coupled spin systems Sebastian Wenderoth, Nathan Ng, Michael Kolodrubetz, Eran Rabani, Michael Thoss In recent years, locally interacting system with static disorder, such as e.g. a random-field Ising chain with nearest neighbour interactions, aroused much attention as these systems can exhibit many-body localization. Many-body localized systems are systems which fail to equilibrate locally under unitary time evolution due to the absence of transport and the emergence of quasi-local integrals of motions, and thus, retaining information about the initial state in local observables. |
Monday, March 15, 2021 12:54PM - 1:06PM Live |
B27.00006: Entanglement Transitions in 2D Random Tensor Networks Ryan Levy, Bryan Clark We numerically study the entanglement phase transition in two-dimensional random tensor networks (Vasseur et al[Phys. Rev. B 100, 134203 (2019)]). We identify the bond-dimension at which the system transitions from area law to volume law scaling and give evidence for either a critical region or phase with logarithmic entanglement entropy scaling. To conclude, we study the scaling properties near the transition using the quantum mutual information. |
Monday, March 15, 2021 1:06PM - 1:18PM Live |
B27.00007: Evading Anderson Localization in a one-dimensional conductor with correlated disorder Onuttom Narayan, Harsh Mathur, Richard Montgomery We show that a one-dimensional disordered conductor with correlated disorder has an extended state and a Landauer resistance that is non-zero in the limit of infinite size in contrast to the predictions of the scaling theory of localization. The delocalization transition is not related to any underlying symmetry of the problem such as particle-hole symmetry in contrast to the handful of known examples of delocalization in one dimension. For a wire of finite length the effect manifests as a sharp transmission resonance that narrows as the length of the wire is increased. Experimental realizations in metamaterials and applications will be discussed, including the possibility of constructing a fault-tolerant narrow-band light filter. |
Monday, March 15, 2021 1:18PM - 1:30PM Live |
B27.00008: Evidence for Quantum Chaos in a One-Dimensional Classically Integrable System Ahmed Elkamshishy, Chris H Greene Resonances in particle transmission through a 1D finite lattice are studied in the presence of a finite number of impurities. Although this is a one-dimensional system that is classically integrable and has no chaos, studying the statistical properties of the spectrum such as the level spacing distribution and the spectral rigidity shows quantum chaos signatures. Using a dimensionless parameter that reflects the degree of state localization, we demonstrate how the transition from regularity to chaos is affected by state localization. The resonance positions and widths are calculated using both the Wigner-Smith time-delay and the Siegert state methods; both show good agreement. Our results are evidence for the existence of quantum chaos in one dimension which is a counter-example to the Bohigas-Giannoni-Schmit conjecture. |
Monday, March 15, 2021 1:30PM - 1:42PM Live |
B27.00009: Fluctuation-dissipation relations as an experimentally accessible indicator for thermalization of disordered quantum spin systems Adrian Braemer, Martin Gaerttner
|
Monday, March 15, 2021 1:42PM - 1:54PM Live |
B27.00010: Many-body delocalization via symmetry emergence. Srivatsa N S, Roderich Moessner, Anne E. B. Nielsen Many-body localization (MBL) provides a mechanism to avoid thermalization in many-body quantum systems. Here, we show that an emergent symmetry can protect a state from MBL. Specifically, we propose a Z2 symmetric model with nonlocal interactions, which has an analytically known, SU(2) invariant, critical ground state. At large disorder strength all states at finite energy density are in a glassy MBL phase, while the lowest energy states are not. These do, however, localize when a perturbation destroys the emergent SU(2) symmetry. The model also provides an example of MBL in the presence of nonlocal, disordered interactions that are more structured than a power law. The presented ideas raise the possibility of an inverted quantum scar', in which a state that does not exhibit area law entanglement is embedded in an MBL spectrum, which does. |
Monday, March 15, 2021 1:54PM - 2:06PM Live |
B27.00011: Many-body flatband localization Carlo Danieli, Alexei Andreanov, Sergej Flach We generate translationally invariant systems exhibiting many-body localization from all-bands-flat single-particle lattice \ |
Monday, March 15, 2021 2:06PM - 2:18PM Live |
B27.00012: Speck of Chaos Lea Santos, Francisco Pérez-Bernal, E. Jonathan Torres Herrera It has been shown that, despite being local, a perturbation applied to a single site of the one-dimensional XXZ model is enough to bring this interacting integrable spin-1/2 system to the chaotic regime. Here, we show that this is not unique to this model, but happens also to the Ising model in a transverse field and to the spin-1 Lai-Sutherland chain. The larger the system is, the smaller the amplitude of the local perturbation for the onset of chaos. We focus on two indicators of chaos, the correlation hole, which is a dynamical tool, and the distribution of off-diagonal elements of local observables, which is used in the eigenstate thermalization hypothesis. Both methods avoid spectrum unfolding and can detect chaos even when the eigenvalues are not separated by symmetry sectors. |
Monday, March 15, 2021 2:18PM - 2:30PM Live |
B27.00013: Dynamics on multiple timescales in centrally coupled disordered spin systems Nathan Ng, Sebastian Wenderoth, Eran Rabani, Michael Thoss, Michael Kolodrubetz Many-body localization, though robust to local perturbations, is not believed to be a stable phase of matter upon introducing infinite range interactions. Such situations naturally arise in systems with central coupling to an auxiliary degree of freedom like a single mode cavity. Here, we consider a 1D disordered Ising chain globally coupled to d-level qudit, which has connections to systems under monochromatic external drive and display Floquet MBL. Through simulations using exact diagonalization and the multilayer multiconfigurational Hartree method, we find that the time evolution can be parsed according multiple timescales, which can be formalized within perturbation theory. Qualitatively, we find changes to the dynamics near a hypothesized breakdown of Floquet physics, leading to different behaviors for spin- and qudit-based observables as well as a logarithmically slow growth of entanglement entropy. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700