Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 65, Number 4
Monday–Friday, June 1–5, 2020; Portland, Oregon
Session N03: Quantum SimulationLive
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Chair: Peter Schauss, University of Virginia Room: D135-136 |
Thursday, June 4, 2020 10:30AM - 10:42AM Live |
N03.00001: Relaxation in an anisotropic Heisenberg model Ivana Dimitrova, Niklas Jepsen, Jesse Amato-Grill, Wen Wei Ho, Mikhail Lukin, Eugene Demler, Wolfgang Ketterle Anisotropic spin couplings in the Heisenberg model break rotational symmetry in spin space. We probe this anisotropy by rotating an initial out-of-equilibrium spin pattern. While longitudinal spin modulations only relax by transport, rotating the initial state introduces a new relaxation mechanism. We find intrinsic local dephasing which can be controlled by the anisotropy, and we directly observe the effective magnetic field term in the Hamiltonian, which has its origin in the mapping from the Hubbard model and which has never been observed before. [Preview Abstract] |
Thursday, June 4, 2020 10:42AM - 10:54AM Live |
N03.00002: Simulation of XXZ Spin Models using Sideband Transitions in Trapped Bosonic Gases Anjun Chu, Johannes Will, Jan Arlt, Carsten Klempt, Ana Maria Rey We theoretically propose and experimentally demonstrate the use of motional sidebands in a trapped ensemble of $^{87}$Rb atoms as a way to engineer tunable long-range XXZ spin models. We benchmark our simulator by probing a ferromagnetic to paramagnetic dynamical phase transition in the collective XXZ model plus additional transverse and longitudinal fields via Rabi spectroscopy. Based on experimental observations, we reconstruct the boundary of the dynamical phases and show good agreement with mean-field theoretical predictions. We also theoretically analyze the achievable spin squeezing in our XXZ simulator, opening the possibilities of using motional sidebands to push the frontiers of metrology via quantum entanglement. [Preview Abstract] |
Thursday, June 4, 2020 10:54AM - 11:06AM Live |
N03.00003: Fast scrambling in a one-dimensional spin chain without random long range interactions Sayan Choudhury, Zehan Li, W. Vincent Liu Scrambling is a dynamical process characterizing how locally stored quantum information becomes inaccessible to local measurements during the time evolution of a quantum many-body system. Fast scrambling is of fundamental importance due to its relation to quantum chaos, thermalization, and holographic duality. Most studies so far require random long range interactions to enable fast scrambling. So, a fundamental question is whether such a class of interactions is crucial for fast scrambling. In this work, we propose a new spin chain model, which exhibits fast scrambling without randomness. The model has two ingredients- nearest neighbor interactions, and infinite range interactions. We find that these two ingredients are sufficient to realize fast scrambling. We quantify the scrambling rate using out-of time-ordered correlators, and show that fast scrambling can be observed over a wide parameter regime. We also discuss how to realize our model in current experimental setups. [Preview Abstract] |
Thursday, June 4, 2020 11:06AM - 11:18AM On Demand |
N03.00004: Efficiency of classical simulations for open-system dynamics of Ising models using quantum trajectories Anupam Mitra, Akimasa Miyake, Ivan Deutsch Quantum simulation of non-equilibrium dynamics in many-body systems is seen to be a near-term goal for Noisy Intermediate Scale Quantum (NISQ) devices. While closed quantum system unitary dynamics can become intractable due to rapid growth of entanglement, in NISQ devices, noise and decoherence will limit this growth. As such, we expect that there exist levels of noise and dissipation for which we can classically simulate the observed dynamics efficiently. We study this in the context of Ising spin chains in 1D. We employ a matrix product state representation and use the quantum trajectory method to solve the master equation. For sufficient decoherence and noise, we study how a truncation of the bond dimension of the tensors leads to an efficient simulation that is a good approximation to the exact dynamics. We find that the complexity of the state representation decreases for larger decoherence rates, while the complexity of the state representation is preserved for smaller decoherence rates, compared to the energy scales of the Hamiltonians. Finally, we study physical implementations of our models based on neutral atoms and superconducting qubit NISQ devices. [Preview Abstract] |
Thursday, June 4, 2020 11:18AM - 11:30AM On Demand |
N03.00005: Quantum measurement-based feedback simulation of complex dynamics of mean-field $p$-spin models Manuel Munoz-Arias, Pablo Poggi, Poul Jessen, Ivan Deutsch We study a method for simulating the nonlinear dynamics of many-body spin systems based on measurement-based feedback. We focus on $p$-spin models describing an Ising-like model on a completely connected graph with $p$-body interactions. These models exhibit diverse critical phenomena. For $p=2$ this recovers the Lipkin-Meshkov-Glick (LMG) model, exhibiting a continuous second-order phase transition between paramagnetic and ferromagnetic phases. For $p>2$, the phase transition is a first order and discontinuous. Our protocol considers the collective spin of an ensemble on $N$ qubits, and approximates the dynamics by weakly measuring one projection of the collective spin, followed by unitary evolution conditioned on the measurement outcome [1]. We numerically explore a variety of dynamical properties of phase transitions for different values of $p$, including our ability to recover the mean-field dynamics, and aspects of spontaneous symmetry breaking induced by the measurement. We characterize the simulated behavior in terms of the number of particles $N$, and study how the dynamics approaches the classical limit. Finally, we propose a possible experimental implementation of our $p$-spin simulation using an atom-light interface. [1] Munoz-Arias et al., arXiv:1907.12606 [Preview Abstract] |
Thursday, June 4, 2020 11:30AM - 11:42AM On Demand |
N03.00006: Factorizability and phase coherence in the anisotropic Heisenberg spin-1/2 XXZ chain in a transverse magnetic field and longitudinal Dzyaloshinskii-Moriya interaction. Durganandini Pillarishetty, Pradeep Thakur We study the entanglement and factorization properties of the Heisenberg spin-1/2 XXZ chain in the presence of a transverse magnetic field and a longitudinal Dzyaloshinskii-Moriya interaction (DMI). We use both numerical and analytic methods for the study. In the absence of the DMI, the ground state is well known to be factorizable at a certain magnetic field strength. The longitudinal DMI destroys the factorizability property; however there exists a magnetic field strength at which the many body ground state has maximal phase coherence. We discuss the connections of factorizability and phase coherence properties to the determination of macroscopic reference frames for the three independent orientations of the quantum spin or qubit degrees of freedom. [Preview Abstract] |
Thursday, June 4, 2020 11:42AM - 11:54AM Not Participating |
N03.00007: Locally addressable cold atomic gas coupled to a high finesse optical cavity Justin Gerber, Emma Deist, Johannes Zeiher, Alec Bohnett, Aron Lloyd, Dan Stamper-Kurn The study of many-body quantum systems via weak measurement and at the single atom level enables better understanding and control of such systems. Here we report on the first calibrations of an experimental apparatus 1) in which an atomic quantum gas is strongly coupled to an optical cavity and 2) with which we will locally address individual components of the gas for read out and control. The interaction of atoms with the photonic modes of a high finesse optical cavity allows for the opportunity to engineer interactions between atomic degrees of freedom as well as the ability to sensitively measure the quantum state of those same degrees of freedom. Local addressability and motional control will be facilitated by projecting tunable microtrap tweezers onto the atoms through a high-resolution objective transverse to the cavity axis. This apparatus presents possibilities to engineer locally controllable many-body Hamiltonians for quantum simulation, to introduce tunable dissipation into the quantum system and to strongly and weakly measure many-body correlation functions. Weak continuous measurement combined with local dynamical control opens the door to many-body quantum feedback to realize techniques for novel state preparation and quantum error correction protocols. [Preview Abstract] |
Thursday, June 4, 2020 11:54AM - 12:06PM |
N03.00008: Flat-band ferromagnetism of SU($N$ Hubbard model on Tasaki lattices Ruijin Liu, Wenxing Nie, Wei Zhang We investigate the para-ferro magnetic transition of the repulsive SU(N) Hubbard model on a type of one- and two-dimensional decorated cubic lattices, referred as Tasaki lattices, which feature massive single-particle ground state degeneracy. Under certain restrictions for constructing localized many-particle ground states of flat-band ferromagnetism, the quantum model of strongly correlated electrons is mapped to a classical statistical geometric site-percolation problem, where the nontrivial weights of different configurations must be considered. We prove rigorously the existence of para-ferro transition for the SU(N) Hubbard model on one-dimensional Tasaki lattice and determine the critical density by the transfer-matrix method. In two dimensions, we numerically investigate the phase transition of SU(3), SU(4) and SU(10) Hubbard models by Metropolis Monte Carlo simulation. We find that the critical density exceeds that of standard percolation, and increases with spin degrees of freedom, implying that the effective repulsive interaction becomes stronger for larger N. We further rigorously prove the existence of flat-band ferromagnetism of the SU(N) Hubbard model when the number of particles equals to the degeneracy of the lowest band in the single-particle energy spectrum. [Preview Abstract] |
Thursday, June 4, 2020 12:06PM - 12:18PM |
N03.00009: Spin transport in a Heisenberg model with negative anisotropy Jesse Amato-Grill, Niklas Jepsen, Ivana Dimitrova, Wen Wei Ho, Mikhail Lukin, Eugene Demler, Wolfgang Ketterle Using ultracold atoms, we experimentally study for the first time a Heisenberg model with negative anisotropy: the longitudinal and transverse couplings in the Hamiltonian have opposite sign. Transport in this system shows qualitatively different behavior compared to positive anisotropy. We observe ballistic transport at short relaxation times and diffusive transport at long relaxation times for all measured negative anisotropies. However, we find that the diffusion coefficient is a strong function of anisotropy. This behavior, reminiscent of transport in a classical gas, is in contrast to the anomalous diffusion we previously observed for positive anisotropies. [Preview Abstract] |
Thursday, June 4, 2020 12:18PM - 12:30PM |
N03.00010: Spin transport in a tunable Heisenberg model Niklas Jepsen, Jesse Amato-Grill, Ivana Dimitrova, Wen Wei Ho, Mikhail Lukin, Eugene Demler, Wolfgang Ketterle We report on the first realization of the anisotropic Heisenberg model using ultracold atoms with fully tunable anisotropy. So far, only the isotropic Heisenberg model had been realized. We demonstrate this tunability by measuring the transport properties of the Hamiltonian as function of anisotropy in 1D-chains. We start with an out-of-equilibrium spin pattern and see how this pattern relaxes. As a function of increasing anisotropy, we observe a ballistic and a diffusive regime, which are smoothly connected by a super-diffusive regime and followed by a sub-diffusive regime. [Preview Abstract] |
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