Bulletin of the American Physical Society
87th annual meeting of the Southeastern Section of the APS
Volume 65, Number 19
Thursday–Friday, November 5–6, 2020; Virtual
Session B02: Quantum Materials and Information |
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Chair: Peizhi Mai, University of TN |
Thursday, November 5, 2020 11:00AM - 11:12AM |
B02.00001: Quantum Wakes in Lattice Fermions Matthew Wampler, Peter Schauss, Eugene Kolomeisky, Israel Klich The wake following a vessel in water is a signature interference effect of moving bodies, and, as described by Lord Kelvin, is contained within a constant universal angle. However, wakes may accompany different kinds of moving disturbances in other situations and even in lattice systems. Here, we investigate the effect of moving disturbances on a Fermi lattice gas of ultracold atoms and analyze the novel types of wake patterns that may occur. We show how at half-filling, the wake angles are dominated by the ratio of the hopping energy to the velocity of the disturbance and on the angle of motion relative to the lattice direction. Moreover, we study the difference between wakes left behind a moving particle detector versus that of a moving potential or a moving particle extractor. We show that these scenarios exhibit dramatically different behavior at half-filling, with the "measurement wake" following an idealized detector vanishing, though the motion of the detector does still leaves a trace through a "fluctuation wake." Finally, we discuss the experimental requirements to observe our predictions in ultracold fermionic atoms in optical lattices. [Preview Abstract] |
Thursday, November 5, 2020 11:12AM - 11:24AM |
B02.00002: Addressing Autocorrelation in the Determinant Quantum Monte Carlo Method Isaac Ownby, Phillip Dee, Steven Johnston Autocorrelation is a prominent issue among all Monte Carlo methods. Autocorrelation times are especially bad when the simulation is close to a phase transition. This issue of "critical slowing" can often be reduced, even eliminated, using cluster algorithms. The algorithms update the degrees of freedom in large clusters or blocks to efficiently kick configurations out of local energy minima. Albeit, the updates often increase the computational cost of the simulation; thus, there is a balance in the minimization of autocorrelation times and runtime. One system with a severe autocorrelation problem is the half-filled 2D Holstein model, which exhibits a metal-to-insulator transition at sufficiently low temperatures. Using determinant quantum Monte Carlo to simulate this model, we study the dependence of the autocorrelation time on the type and frequency of MC updates as well as other simulation parameters. Our results suggest some useful ways to tune MC updates to yield shorter autocorrelation times without resorting to the overly expensive simulations. [Preview Abstract] |
Thursday, November 5, 2020 11:24AM - 11:36AM |
B02.00003: Higher-Order Topology and Defect States in the Charge-Density-Wave Phase of (TaSe$_4$)$_2$I Meng Hua, Brian Khor, Yichen Hu, Benjamin J. Wieder, Jeffrey C. Y. Teo Recent theoretical and experimental investigations have identified the quasi-1D compound (TaSe$_4$)$_2$I as hosting a Weyl semimetal phase that becomes gapped by an incommensurate charge-density wave (CDW) just below room temperature. Though the CDW phase have been shown to exhibit incipient experimental signatures of (valley-) axion electrodynamics, however, the bulk topology of the insulating CDW state remains an open question. In this talk, we present a physically motivated, lattice-commensurate coupled-wire model based on Topological Quantum Chemistry and crystalline symmetry that approximates the CDW phase of (TaSe$_4$)$_2$I. We demonstrate that our model hosts several higher-order and weak topological phases, depending on the pinned values of several symmetry-allowed mass terms, which we link to independent CDW phase angles $\phi$. We also present evidence for helical modes bound to real-space disclinations and mass vortices in the CDW state. [Preview Abstract] |
Thursday, November 5, 2020 11:36AM - 11:48AM |
B02.00004: NISQ-era Simulations of Quantum Many-Body Dynamics Britta Manifold, Cheng-Chien Chen Recent advancements in universal quantum computer technologies have raised the possibility of leveraging the so-called ”quantum advantage” to approach classically intractable problems. For simulations of quantum many-body systems, there is great potential to meet this goal in the near future. Here, we focus on small clusters of interacting spin models and perform time evolution calculations in the quantum circuit paradigm using IBM’s superconducting qubit platform. We compare and analyze the noisy and exact dynamics of total magnetization, n-point correlation functions, occupation probabilities, and excitation spectra. We repeat these circuits under various magnetic and spatial regimes, and under the influence of external perturbations. We also explore different error mitigation methods in order to enhance quantitative accuracy. [Preview Abstract] |
Thursday, November 5, 2020 11:48AM - 12:00PM |
B02.00005: Many-Body Thermodynamics on Quantum Computers via Partition Function Zeros Akhil Francis, Daiwei Zhu, Cinthia Huerta Alderete, Sonika Johri, Xiao Xiao, James K. Freericks, Christopher Monroe, Norbert M. Linke, Alexander F. Kemper Partition functions are ubiquitous in physics: they are important in determining the thermodynamic properties of many-body systems, and in understanding their phase transitions. As shown by Lee and Yang, analytically continuing the partition function to the complex plane allows us to obtains its zeros and thus the entire function. Moreover, the scaling and nature of these zeros can elucidate phase transitions. Here we show how to find partition function zeros on noisy intermediate-scale trapped ion quantum computers in a scalable manner, using the XXZ model as a prototype. We illustrate the transition from XY-like behavior to Ising-like behavior as a function of the anisotropy. While quantum computers cannot yet scale to the thermodynamic limit, our work provides a pathway to do so as hardware improves, allowing the determination of critical phenomena for systems that cannot be solved otherwise. [Preview Abstract] |
Thursday, November 5, 2020 12:00PM - 12:12PM |
B02.00006: Coherence of Interacting Qubits in a Common Environment Juan Pablo Speer, Ryoichi Kawai The standard theory of thermodynamics states that a quantum system in contact with a thermal environment relaxes to the equilibrium state known as the Gibbs state. This interaction causes decoherence of the system. However, if a system consists of coupled parts, interaction with a thermal environment does not necessarily lead to decoherence for all energy states. Here we considered a system of two interacting qubits, both independently interacting with the same bosonic environment and numerically simulated the dynamics of the system using the hierarchical equation of motion. We show that if the interaction between each qubit and the environment is symmetric, a decoherence-free state (DFS) exists. We explore the stability of the DFS by varying the strength and type of coupling between the qubits and the thermal bath. [Preview Abstract] |
Thursday, November 5, 2020 12:12PM - 12:24PM |
B02.00007: Heat Conduction Through a Pair of Quantum Entangled Qubits Tharon Holdsworth, Ryoichi Kawai The second law of thermodynamics states that in the absence of external influence, heat flows spontaneously from a hot body to a cold body. However, when heat flows through a quantum system, the direction of transient heat can be reversed without violating the second law by utilizing internal quantum entanglement as resources. We consider a pair of qubits independently in contact with a hot heat bath and a cold heat bath. An initial state is created such that each qubit is in local thermal equilibrium with the corresponding heat bath and the qubits are quantum mechanically entangled without disturbing this local equilibrium state. The time evolution of the entanglement and heat flow through the qubits is investigated by numerically simulating the dynamics of the total system density matrix using hierarchical equations of motion. [Preview Abstract] |
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