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 U10: Quantum Simulation IILive
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Chair: Raphael Pooser, ORNL |
Thursday, June 3, 2021 2:00PM - 2:12PM Live |
U10.00001: Symmetry breaking and error correction in open quantum systems Simon Lieu, Ron Belyansky, Jeremy T Young, Rex O Lundgren, Victor V Albert, Alexey V Gorshkov Symmetry-breaking transitions are a well-understood phenomenon of closed quantum systems in quantum optics, condensed matter, and high energy physics. However, symmetry breaking in open systems is less thoroughly understood, in part due to the richer steady-state and symmetry structure that such systems possess. For the prototypical open system - a Lindbladian - a unitary symmetry can be imposed in a "weak" or a "strong" way. We characterize the possible Zn symmetry breaking transitions for both cases. In the case of Z2, a weak-symmetry-broken phase guarantees at most a classical bit steady-state structure, while a strong-symmetry-broken phase admits a partially-protected steady-state qubit. Viewing photonic cat qubits through the lens of strong-symmetry breaking, we show how to dynamically recover the logical information after any gap-preserving strong-symmetric error; such recovery becomes perfect exponentially quickly in the number of photons. Our study forges a connection between driven-dissipative phase transitions and error correction. |
Thursday, June 3, 2021 2:12PM - 2:24PM Live |
U10.00002: Dark states from superradiant decay of multilevel atoms in a cavity Asier Pineiro Orioli, James K Thompson, Ana Maria Rey We investigate the collective decay dynamics of atoms with a generic multilevel structure (F → F') coupled to two light modes of different polarization inside a cavity. Due to the multiple decay channels, the eigenstate structure and superradiant behavior is much richer and more complex than for two-level atoms. In particular, we find that, in contrast to the two-level case, multilevel atoms can harbour eigenstates that are perfectly dark to cavity decay even within the subspace of permutationally symmetric states (collective Dicke manifold). As a consequence, the superradiant decay of multilevel atoms can end up stuck in one of these dark states, where a macroscopic fraction of the atoms remains excited. These dark states should be readily observable in current optical cavity experiments with alkaline-earth atoms or Raman-dressed transitions. Their long-lived nature anticipates potential applications in quantum sensing and metrology, and quantum simulation. |
Thursday, June 3, 2021 2:24PM - 2:36PM Live |
U10.00003: Controlling a qubit stored in a driven-dissipative collective multi-level spin Jeremy T Young, Asier Pineiro Orioli, James K Thompson, Ana Maria Rey In many-body quantum systems, the system-bath coupling often destroys important quantum information and correlations; however, an increasing amount of research has been devoted to harnessing the effects of the bath rather than reducing them. In this talk, I will discuss the possibility of storing, reading, and manipulating a qubit stored in a driven-dissipative collective multi-level spin. This is achieved via the presence of a strong symmetry, which is a symmetry that commutes with both the Hamiltonian and the dissipative jump operators. Due to the fact that the dissipation commutes with the symmetry, quantum information can be preserved indefinitely in the symmetry-broken phase. |
Thursday, June 3, 2021 2:36PM - 2:48PM Live |
U10.00004: Simulating the complete quantum mechanics of very large driven-dissipative Bose-Hubbard systems Piotr Deuar, Alex Ferrier, Giuliano Orso, Michał Matuszewski, Marzena Szymańska Phase-space descriptions of open quantum systems allow for linear or log-linear scaling of computational difficulty with system size, and adaptability to non-uniform and time-dependent systems. They also allow for straightforward calculation of many of the multi-time correlations of interest by replacing Heisenberg operators with he bare time-dependent stochastic variables. |
Thursday, June 3, 2021 2:48PM - 3:00PM Live |
U10.00005: Driven-dissipative creation of a topologically ordered state (AKLT state) Vaibhav Sharma, Erich J Mueller Dissipation in an open quantum system often destroys a quantum state of interest, but if carefully engineered, it can be used as a tool to prepare interesting quantum states. We propose an experimentally viable method to dissipatively create the AKLT (Affleck-Lieb-Kennedy-Tasaki) state which exhibits symmetry protected topological order and harbours gapped edge modes. We analyze a system of bosons trapped in a tilted optical lattice, driven by coherent Raman beams and coupled to a superfluid bath. We propose a protocol under which the AKLT state emerges as the steady state. We use exact diagonalization and DMRG methods to calculate the time scale for state preparation and find that the state preparation time scales quadratically with the system size. |
Thursday, June 3, 2021 3:00PM - 3:12PM Live |
U10.00006: Few-qubit quantum refrigerator for cooling a multi-qubit system Onat Arisoy, Ozgur E Mustecaplioglu We propose to use a few-qubit system as a compact quantum refrigerator for cooling an interacting multi-qubit system. We specifically consider a central qubit coupled to N ancilla qubits in a so-called spin-star model as our quantum refrigerator. We first show that if the interaction between the qubits is of the longitudinal and ferromagnetic Ising model form, the central qubit is colder than the environment. The colder central qubit is then proposed to be used as the refrigerant interface of the quantum refrigerator to cool down general quantum many-qubit systems. We discuss a simple refrigeration cycle, considering the operation cost and cooling efficiency, which can be controlled by N and the qubit-qubit interaction strength. Besides, bounds on the achievable temperature are established. Such few-qubit compact quantum refrigerators can be significant to reduce dimensions of quantum technology applications, can be easy to integrate into all-qubit systems, and can increase the speed and power of quantum computing and thermal devices. |
Thursday, June 3, 2021 3:12PM - 3:24PM Live |
U10.00007: Deterministic fast scrambling with Rydberg arrays Gregory Bentsen, Tomohiro Hashizume, Sebastian Weber, Andrew Daley Fast scramblers are quantum many-body systems that rapidly delocalize quantum information on a timescale that grows logarithmically with the system size N, thereby effectively protecting quantum information from single-qubit errors using the fewest 2-body interactions possible. Here we show how to construct deterministic fast scrambling quantum circuits in near-term experiments with neutral atoms in optical lattices. We show that three experimental tools – nearest-neighbor Rydberg interactions, global single-qubit rotations, and shuffling operations facilitated by an auxiliary tweezer array – are sufficient to generate nonlocal interaction graphs capable of scrambling quantum information using only O(log N) parallel applications of nearest-neighbor gates. We characterize the scrambling properties of these circuits using the Hayden-Preskill thought experiment, and show that these circuits may be harnessed to protect quantum information from multi-qubit erasure even in the presence of realistic levels of dissipation expected in near-term experimental platforms. |
Thursday, June 3, 2021 3:24PM - 3:36PM Live |
U10.00008: Generating Page-scrambled states and teleporting quantum information with engineered fast scramblers Tomohiro Hashizume, Gregory Bentsen, Sebastian Weber, Andrew Daley Page-scrambled states are pure quantum states in which every subsystem, A, up to |A| < N/2 for an N-component system exhibits maximal entanglement entropy. We show that such states can be generated deterministically with O[log(N)] operations in a family of quantum circuits that can be implemented, e.g., using neutral atom arrays and Rydberg excitations. We discuss how these dynamics can be a resource to investigate many-body quantum teleportation following a protocol proposed by Yoshida and Yao in the context of a Hayden-Preskill experiment. We conclude that this family of circuits can outperform circuits with only local interactions, producing higher recovered fidelities especially in the presence of noise, and scrambles as efficiently as randomly coupled qubits. |
Thursday, June 3, 2021 3:36PM - 3:48PM Live |
U10.00009: Z2 lattice gauge theories and Kitaev's toric code: A scheme for analog quantum simulation Lukas Homeier Kitaev's toric code is an exactly solvable model with Z2-topological order, which has potential applications in quantum computation and error correction. However, a direct experimental realization remains an open challenge. Here, we propose a building block for Z2 lattice gauge theories coupled to dynamical matter and demonstrate how it allows for an implementation of the toric-code ground state and its topological excitations. This is achieved by introducing separate matter excitations on individual plaquettes, whose motion induce the required plaquette terms. The proposed building block is realized in the second-order coupling regime and is well suited for implementations with superconducting qubits. Furthermore, we propose a pathway to prepare topologically non-trivial initial states during which a large gap on the order of the underlying coupling strength is present. This is verified by both analytical arguments and numerical studies. Moreover, we outline experimental signatures of the ground-state wavefunction and introduce a minimal braiding protocol. Detecting a pi-phase shift between Ramsey fringes in this protocol reveals the anyonic excitations of the toric-code Hamiltonian in a system with only three triangular plaquettes. Our work paves the way for realizing non-Abelian anyons in analog quantum simulators. |
Thursday, June 3, 2021 3:48PM - 4:00PM Live |
U10.00010: Many-body quantum teleportation via operator spreading in the traversable wormhole protocol Thomas Schuster, Bryce H Kobrin, Ping Gao, Iris Cong, Emil T Khabiboulline, Norbert M Linke, Mikhail Lukin, Christopher R Monroe, Beni Yoshida, Norman Y Yao By leveraging shared entanglement between a pair of qubits, one can teleport a quantum state from one particle to another. Recent advances have uncovered an intrinsically many-body generalization of quantum teleportation, with an elegant and surprising connection to gravity. In particular, the teleportation of quantum information relies on many-body dynamics, which originate from strongly-interacting systems that are holographically dual to gravity; from the gravitational perspective, such quantum teleportation can be understood as the transmission of information through a traversable wormhole. Here, we propose and analyze a new mechanism for many-body quantum teleportation -- dubbed peaked-size teleportation. Intriguingly, peaked-size teleportation utilizes precisely the same type of quantum circuit as traversable wormhole teleportation, yet has a completely distinct microscopic origin: it relies upon the spreading of local operators under generic thermalizing dynamics and not gravitational physics. We demonstrate the ubiquity of peaked-size teleportation, both analytically and numerically, across a diverse landscape of physical systems, including random unitary circuits, the Sachdev-Ye-Kitaev model (at high temperatures), one-dimensional spin chains and a bulk theory of gravity with stringy corrections. Our results pave the way towards using many-body quantum teleportation as a powerful experimental tool for: (i) characterizing the size distributions of operators in strongly-correlated systems and (ii) distinguishing between generic and intrinsically gravitational scrambling dynamics. To this end, we provide a detailed experimental blueprint for realizing many-body quantum teleportation in both trapped ions and Rydberg atom arrays; effects of decoherence and experimental imperfections are analyzed. |
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