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 S10: Quantum Simulation ILive
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Chair: Dan Cole, NIST |
Thursday, June 3, 2021 10:30AM - 10:42AM Live |
S10.00001: Error Scaling with System Size in Digital Quantum Simulations Natalie Pearson, Matthias Troyer, David Poulin In order to meaningfully compare the feasibility of implementing quantum simulation on analogue and digital platforms we must take into account the errors introduced by decomposing the simulation into gate operations for digital computation. The most common implementation uses the Trotter decomposition to map an arbitrary Hamiltonian onto realisable gates. However, the proven upper bounds on the error introduced using this method grows with the system size. In order to maintain the same accuracy for larger systems this would imply a corresponding increase in the number of gates required. We show empirically that for local Hamiltonians the error for local observables and their correlation functions is independent of system size even at the critical point and that for non-local observables away from the critical point this remains true. |
Thursday, June 3, 2021 10:42AM - 10:54AM Live |
S10.00002: Transverse spin dynamics in the anisotropic Heisenberg model realized with ultracold atoms Niklas Jepsen, Wen Wei Ho, Jesse Amato-Grill, Ivana Dimitrova, Eugene Demler, Wolfgang Ketterle Anisotropic spin couplings in the Heisenberg model break spin-rotational symmetry. Transverse spin components are no longer conserved and can decay not only by transport, but also by dephasing. Here we utilize ultracold atoms to simulate the dynamics of 1D Heisenberg spin chains, and observe fast, local spin decay controlled by the anisotropy. Additionally, we directly observe an effective magnetic field created by superexchange which causes an inhomogeneous decay mechanism due to variations of lattice depth between chains, as well as a homogeneous dephasing mechanism due to the twofold reduction of the effective magnetic field at the edges of the chains and due to fluctuations of the effective magnetic field in the presence of mobile holes. The latter is a new coupling mechanism between holes and magnons. All these dephasing mechanisms have not been observed before with ultracold atoms and illustrate basic properties of the underlying Hubbard model. |
Thursday, June 3, 2021 10:54AM - 11:06AM Live |
S10.00003: Realization of para-particle oscillators in trapped ions Cinthia Huerta Alderete, Alaina Green, Nhung Nguyen, Yingyue Zhu, Blas Manuel Rodríguez Lara, Norbert M Linke
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Thursday, June 3, 2021 11:06AM - 11:18AM Live |
S10.00004: Observation of Stark many-body localization without disorder William N Morong, Fangli Liu, Patrick M Becker, Kate S Collins, Lei Feng, Antonis Kyprianidis, Guido Pagano, Tianyu You, Alexey V Gorshkov, Christopher R Monroe Thermalization is a ubiquitous process of statistical physics, in which details of few-body observables are washed out in favor of a featureless steady state. Even in isolated quantum many-body systems, limited to reversible dynamics, thermalization typically prevails. However, in these systems, there is another possibility: many-body localization (MBL) can result in preservation of a non-thermal state. While disorder has long been considered an essential ingredient for this phenomenon, recent theoretical work has suggested that a quantum many-body system with a uniformly increasing field -- but no disorder -- can also exhibit MBL, resulting in `Stark MBL.' Here we realize Stark MBL in a trapped-ion quantum simulator and demonstrate its key properties: halting of thermalization and slow propagation of correlations. Tailoring the interactions between ionic spins in an effective field gradient, we directly observe their microscopic equilibration for a variety of initial states, and we apply single-site control to measure correlations between separate regions of the spin chain. Further, by engineering a varying gradient, we create a disorder-free system with coexisting long-lived thermalized and nonthermal regions. The results demonstrate the unexpected generality of MBL, with implications about the fundamental requirements for thermalization and with potential uses in engineering long-lived non-equilibrium quantum matter. |
Thursday, June 3, 2021 11:18AM - 11:30AM Live |
S10.00005: Programmable Interactions and Emergent Geometry in a 1D Array of Atomic Ensembles Avikar Periwal, Eric S Cooper, Philipp Kunkel, Emily J Davis, Julian F Wienand, Monika H Schleier-Smith Tunable interactions are essential for building flexible platforms for quantum computation and simulation. We couple a 1D array of atomic ensembles to an optically driven cavity, generating an XY Hamiltonian. Precise control of magnetic field gradients and drive field modulation allow us to engineer spin-spin couplings with arbitrary dependence of the amplitude and phase on distance. This enables us to implement the XY Hamiltonian on a variety of different geometries, including 2D surfaces and a Moebius ladder. State-sensitive in-situ imaging of the individual ensembles allows us to directly reconstruct the effective Hamiltonian's dispersion relation, as well as the programmed geometry. These highly programmable interactions anticipate further study of frustrated systems, fast scrambling, and designer Hamiltonians for quantum-enhanced precision measurement. |
Thursday, June 3, 2021 11:30AM - 11:42AM Live |
S10.00006: Discrete time-crystalline order enabled by quantum many-body scars: entanglement steering via periodic driving Nishad Maskara, Alexios Michailidis, Wen Wei Ho, Dolev Bluvstein, Soonwon Choi, Mikhail Lukin, Maksym Serbyn The control of many-body quantum dynamics in complex systems is a key challenge in the quest to reliably produce and manipulate large-scale quantum entangled states. Recently, quench experiments in Rydberg atom arrays (Bluvstein et al. Science, 25 Feb 2021) demonstrated that coherent revivals associated with quantum many-body scars can be stabilized by periodic driving, generating stable subharmonic responses over a wide parameter regime. We analyze a simple, related model where these phenomena originate from spatiotemporal ordering in an effective Floquet unitary, corresponding to discrete time-crystalline (DTC) behavior in a prethermal regime. Unlike conventional DTC, the subharmonic response exists only for Neel-like initial states, associated with quantum scars. We predict robustness to perturbations and identify emergent timescales that could be observed in future experiments. Our results suggest a route to controlling entanglement in interacting quantum systems by combining periodic driving with many-body scars. |
Thursday, June 3, 2021 11:42AM - 11:54AM Live |
S10.00007: Detecting quantum phase transitions via out-of-time-ordered correlators without time reversal Sean R Muleady, Robert J Lewis-Swan, Ana Maria Rey We propose a dynamical method to connect quantum phase transitions (QPTs) and quantum coherence via out-of-time-ordered correlators (OTOCs), which measure the spread of quantum information in a many-body system. Using iconic examples of QPTs, we show that an abrupt change in coherence and entanglement of the ground state across a QPT is observable in the spectrum of multiple quantum coherences, a special type of OTOC first developed in NMR spectroscopy. We develop a robust protocol to obtain the relevant OTOCs using quasi-adiabatic ramps, alleviating the need for time reversal of coherent dynamics [1]. Our protocol is applicable for a broad range of current experiments in trapped ions and optical tweezer arrays. |
Thursday, June 3, 2021 11:54AM - 12:06PM Live |
S10.00008: Driven-dissipative dynamics in superconducting circuit lattices coupled to quantum baths Ruichao Ma, Botao Du, Jeremy Cadiente, Ramya Suresh Superconducting circuits have emerged as a powerful platform for quantum computing and simulation. The long coherence, strong interactions, and high tunability e.g. of coupling to the environment, make circuits ideal for exploring novel quantum many-body phases in open quantum systems. Recently, engineered dissipation is used to prepare a Mott insulator of photons in circuits by coupling a narrowband incoherent bath with a Bose-Hubbard lattice. Here, we propose experiments to explore strongly correlated lattice phases in the presence of broadband quantum baths. We discuss schemes for realizing dissipative baths with dynamically tunable spectra, and show how they can be used to create and manipulate strongly entangled lattice phases. The non-equilibrium dynamics of quantum correlations can be probed directly using site-resolved readout. The engineered baths also allow us to explore the effect of non-classical noise on interacting quantum systems. We will present results from numerical simulations and our experimental progress. |
Thursday, June 3, 2021 12:06PM - 12:18PM Live |
S10.00009: Observation of a prethermal discrete time crystal Antonis Kyprianidis, Francisco Machado, William N Morong, Patrick M Becker, Kate S Collins, Dominic Else, Lei Feng, Paul W Hess, Chetan Nayak, Guido Pagano, Norman Y Yao, Christopher R Monroe The conventional framework for defining and understanding phases of matter requires thermodynamic equilibrium. Extensions to non-equilibrium systems have led to surprising insights into the nature of many-body thermalization and the discovery of novel phases of matter, often catalyzed by driving the system periodically. The inherent heating from such Floquet drives can be tempered by including strong disorder in the system, but this can also mask the generality of non-equilibrium phases. In this work, we utilize a trapped-ion quantum simulator to observe signatures of a non-equilibrium driven phase without disorder: the prethermal discrete time crystal (PDTC). Here, many-body heating is suppressed not by disorder-induced many-body localization, but instead via high-frequency driving, leading to an expansive time window where non-equilibrium phases can emerge. We observe a number of key features that distinguish the PDTC from its many-body-localized disordered counterpart, such as the drive-frequency control of its lifetime and the dependence of time-crystalline order on the energy density of the initial state. Floquet prethermalization is thus presented as a general strategy for creating, stabilizing and studying intrinsically out-of-equilibrium phases of matter. |
Thursday, June 3, 2021 12:18PM - 12:30PM Live |
S10.00010: Floquet Hamiltonian Engineering of an Isolated Many-Body Spin System Sebastian Geier, Nithiwadee Thaicharoen, Clement Hainaut, Titus Franz, Andre Salzinger, Annika Tebben, David Grimshandl, Gerhard Zuern, Matthias Weidemüller Controlling interactions is the key element for quantum engineering of many-body systems. Using time-periodic driving, a naturally given many-body Hamiltonian of a closed quantum system can be transformed into an effective target Hamiltonian thus exhibiting vastly different dynamics. We demonstrate such Floquet engineering with a system of spins represented by Rydberg states in an ultracold atomic gas. Applying a sequence of spin manipulations, the anisotropy of the effective Heisenberg XXZ Hamiltonian can be continuously tuned resulting in a change of symmetry. As a consequence, we observe a drastic change of the relaxation behavior of the total spin which is qualitatively captured by a semi-classical simulation. Synthesising a wide range of Hamiltonians in a single experimental setting opens new opportunities for quantum simulation of non-equilibrium dynamics. |
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