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 R27: Disorder and Localization in AMO Systems IILive

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Sponsoring Units: DAMOP DCMP Chair: Bumho Kim, University of Pennsylvania 
Thursday, March 18, 2021 8:00AM  8:36AM Live 
R27.00001: Disordered fermions in optical lattices Invited Speaker: Brian DeMarco Multiple pioneering works in the subject 
Thursday, March 18, 2021 8:36AM  8:48AM Live 
R27.00002: Super Hamiltonian method for twodimensional quasicrystals Callum Duncan, Manuel Valiente The understanding of the physical properties of quasicrystals is far less than that of their structure. However, recent experimental realisations of aperiodic systems in ultracold atom and photonic settings heralds a new stage in their study. To characterise and investigate these systems, new efficient methods of calculating their properties are required. An approach which is tailored to aperiodic systems was recently introduced [M Valiente, C W Duncan, and N T Zinner, arXiv:1908.03214]. This new technique relies on the extension of the problem to a higherdimensional space, transforming the Hamiltonian into a super Hamiltonian. In this work, we extend this approach to 2D and consider an example of an 8fold symmetric potential. We show that the singleparticle states and spectra can be obtained and calculate the localisationdelocalisation critical point and scaling. The super Hamiltonian approach can be easily extended to study e.g. the presence of a magnetic field and is a useful future tool for studying the physics of aperiodic systems. 
Thursday, March 18, 2021 8:48AM  9:00AM Live 
R27.00003: Postselectionfree entanglement dynamics via spacetime duality Matteo Ippoliti, Vedika Khemani The dynamics of entanglement in `hybrid' circuits (involving both unitary gates and quantum measurements) has recently become an object of intense study. A major hurdle toward experimentally realizing this physics is the need to apply postselection on random measurement outcomes in order to repeatedly prepare a given output state, resulting in an exponential overhead. We propose a method to sidestep this issue in a wide class of nonunitary circuits by taking advantage of spacetime duality. This method maps the purification dynamics of a mixed state under nonunitary evolution onto a particular correlation function in an associated unitary circuit, and translates to an operational protocol which could be straightforwardly implemented on a digital quantum simulator. We discuss the signatures of different entanglement phases, and demonstrate examples via numerical simulations. 
Thursday, March 18, 2021 9:00AM  9:12AM Live 
R27.00004: Perturbative instability of nonergodic phases in nonAbelian quantum chains Brayden Ware, Dmitry Abanin, Romain Vasseur An important challenge in the field of manybody quantum dynamics is to identify nonergodic states of matter beyond manybody localization (MBL). Strongly disordered spin chains with nonAbelian symmetry and chains of nonAbelian anyons are natural candidates, as they are incompatible with standard MBL. In such chains, real space renormalization group methods predict a partially localized, nonergodic regime known as a quantum critical glass (a critical variant of MBL). We argue that such tentative nonergodic states are perturbatively unstable using an analytic computation of the scaling of offdiagonal matrix elements and accessible level spacing of local perturbations. Our results indicate that strongly disordered chains with nonAbelian symmetry display either spontaneous symmetry breaking or ergodic thermal behavior at long times; we identify the relevant length and time scales for thermalization. 
Thursday, March 18, 2021 9:12AM  9:24AM Live 
R27.00005: Persistence of correlations in manybody localized spin chains Vasilii Vadimov, Tapio AlaNissila, Mikko Möttönen We study the evolution and persistence of quantum and classical correlations between spatially separated sites in the disordered XXZ spin chain in its ergodic and manybodylocalized phases using exact diagonalization and matrix product state simulations. We show that in the manybodylocalized phase quantum entanglement survives in longtime limit, compared to exchange time, even though it is suppressed much stronger than the classical correlations. We study the residual entanglement and correlations as functions of the system size and on the disorder strength. Finally, we demonstrate the robustness of entanglement and correlations with respect to local dissipation in the bulk of the system. Thus, our studies suggest that the manybody localized phase is potentially useful for building quantum memory where distant qubits may be entangled. 
Thursday, March 18, 2021 9:24AM  9:36AM Live 
R27.00006: Many Body Localization Transition in Quasiperiodic Systems Hansveer Singh, Brayden Ware, Sarang Gopalakrishnan, Romain Vasseur We study the many body localization transition in an XXZ spin chain subject to a quasiperiodic field by examining the structure of the local conserved quantities (lbits) in the phase diagram. We construct lbits by evolving local operators by the Hamiltonian and averaging over time. Motivated by the noninteracting transition that occurs in this model, we consider the weight of the lbit on two body fermion operators and show that this two body weight contains the dominate contributions to the lbit in the thermal phase. Further, we show that these contributions arise from hydrodynamic modes in the model. By subtracting the projection onto the hydrodynamic modes from the lbits, we obtain a quantity that is sensitive to the localization transition. We find that the transition occurs at stronger quasiperiodic modulations and has a larger critical exponent than previously estimated, while other estimates are affected by strong finite size effects. 
Thursday, March 18, 2021 9:36AM  9:48AM Live 
R27.00007: Manybody localization of quantized plasmonic excitations in disordered 1D atomic chains Emily Townsend, Markyves Gaunin, Garnett Bryant Short onedimensional atom chains halffilled with Coulombically interacting electrons support quantized plasmonic excitations as their low energy excited states. Excitations can be launched by coupling the chain to quantum emitters. Our simulations with extendedrange Hubbard models reveal how excitations can be transferred between emitters at opposite ends of the chain via the plasmonic excitations on the chain and how this depends on the range of the electronelectron interaction on the chain. Positional disorder in the chain provides an ideal testbed for studying the onset of manybody localization (MBL) and how MBL affects information transfer across the chain. We show how the MBL develops with disorder and how it influences the time evolution of plasmonic excitations launched on disordered chains. Plasmons can also be used to induce entanglement between excitations on the quantum emitters. We show how the entanglement generation is related to the MBL as excitations are launched across the chain. 
Thursday, March 18, 2021 9:48AM  10:00AM Live 
R27.00008: Cavity induced Manybody localization Rongchun Ge, Michael Kolodrubetz

Thursday, March 18, 2021 10:00AM  10:12AM Live 
R27.00009: Static and dynamical properties of a onedimensional model with longrange couplings Isaías Vallejo, Germán LunaAcosta, E. Jonathan Torres Herrera Quantum systems can be characterized by studying its static and dynamical properties. Some of these properties are related, for example, correlations between energy levels are manifested as a “hole” in the dynamics of the survival probability (SP), also the saturation value of SP coincides with the inverse participation ratio of the initial state. These facts let us infer some results of the dynamics by studying the static properties and vice versa. We will present our studies about the onedimensional Anderson model with long range couplings. Specifically, we explore how the properties of the system depend on the range of the couplings, disorder strength and system size. In particular, by means of the survival probability and the imbalance, we present an analysis of two relevant time scales, the Thouless time and the saturation time. 
Thursday, March 18, 2021 10:12AM  10:24AM Live 
R27.00010: Multifractality and selfaveraging at the manybody localization transition Andrei Solórzano, E. Jonathan Torres Herrera, Lea Santos

Thursday, March 18, 2021 10:24AM  10:36AM Live 
R27.00011: Complex network description of phase transitions in the classical and quantum disordered Ising Model Mina Fasihi, Guillermo Garcia Perez, Sabrina Maniscalco, Lincoln D Carr Complex network analysis is a powerful tool to describe and characterize classical systems such as the Ising model in a transverse magnetic field. Measuring spinspin correlations gives rise to the adjacency matrix, representing a weighted network. In this study, the spinspin correlations at different temperatures are analytically calculated, yielding phasedependent complex networks, from simple networks in the low temperature ferromagnetic limit to random ones at high temperature. The network structure varies as the transverse field and temperature change, recovering the phase diagram and providing initial insight into correlations in the critical region. Analyzing the resulting complex network using a variety of network measures such as the degree histogram, average clustering, betweenness centrality and the graph entropy, the complexity is characterized. This method is applied for both the disordered classical Ising and quantum Ising lattice, demonstrating the role of finite temperature and disorder in generation of complexity. 
Thursday, March 18, 2021 10:36AM  10:48AM Live 
R27.00012: Numerical evidence for a manybody localization transition in two dimensions Nyayabanta Swain, HoKin Tang, Brian Khor, Fakher Assaad, Shaffique Adam, Pinaki Sengupta We use the stochastic series expansion quantum Monte Carlo method, together with the eigenstatetoHamiltonian mapping approach, to probe the manybody localization transition in the two dimensional spinhalf Heisenberg model with magnetic disorder. We establish the localised nature of the ground state by studying the spin stiffness, local entanglement entropy, and local magnetization. By mapping the ground state of this parent Hamiltonian to excited states of target Hamiltonians, we determine the manybody localized regime in an energyresolved phase diagram. Our study presents concrete numerical evidence for the existence of a manybody localized phase in two dimensions. 
Thursday, March 18, 2021 10:48AM  11:00AM Live 
R27.00013: Manybody localization in a disordered quantum dimer model on the honeycomb lattice Francesca Pietracaprina, Fabien Alet We numerically study the possibility of manybody localization transition in a disordered quantum dimer model on the honeycomb lattice. 
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