Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D34: Trapped Ion and Cold Atom Qubits IFocus Recordings Available
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Sponsoring Units: DQI DAMOP Chair: Petar Jurcevic, IBM Room: McCormick Place W-193A |
Monday, March 14, 2022 3:00PM - 3:36PM |
D34.00001: Programmable quantum circuits with an array of nuclear spins Invited Speaker: Jacob Covey Arrays of neutral atoms with Rydberg-mediated interactions have emerged as a promising platform for myriad quantum science applications. More recently, alkaline earth(-like) atoms (AEAs) arrays have expanded the neutral atom toolbox by offering new techniques for the control of Rydberg states and new opportunities for metrology via the emerging “atom array optical clocks”. To date, most of the work with AEA arrays has used isotopes with zero nuclear spin. In this talk, I will describe our efforts to utilize arrays of ytterbium-171 (Yb-171) atoms to leverage their nuclear spin-1/2 degree of freedom for new opportunities in quantum computing and networking. |
Monday, March 14, 2022 3:36PM - 3:48PM |
D34.00002: Quantum Register of Fermion Pairs Botond Oreg, Thomas R Hartke, Carter Turnbaugh, Ningyuan Jia, Martin W Zwierlein Quantum control of motion enables protocols to process and distribute quantum information and allows probing entanglement in correlated states of matter. However, motional coherence of individual particles can be fragile to maintain. Systems in nature with robust motional coherence instead often involve pairs of particles, such as Cooper pairs. Here we demonstrate long-lived motional coherence and entanglement of pairs of fermionic atoms in an optical lattice array. The common and relative motion of each pair realize a robust qubit, protected by exchange symmetry. The energy difference between the two motional states is set by the atomic recoil energy, only dependent on mass and lattice wavelength. We observe quantum coherence beyond ten seconds. Modulating interactions between the atoms provides universal control of the motional qubit. The methods presented here open the door towards coherently programmable quantum simulators of many-fermion systems, and, by implementing further advances, digital quantum computation employing fermion pairs. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D34.00003: A dual-element, two-dimensional atom array with continuous-mode operation Kevin Singh, Shraddha Anand, Andrew Pocklington, Jordan Kemp, Hannes Bernien Quantum processing architectures that include multiple qubit modalities offer compelling strategies for high-fidelity operations and readout, quantum error correction, and a path for scaling to large system sizes. Such hybrid architectures have been realized for leading platforms, including superconducting circuits and trapped ions. Recently, a new approach for constructing large, coherent quantum processors has emerged based on arrays of individually trapped neutral atoms. However, these demonstrations have been limited to arrays of a single atomic element where the identical nature of the atoms makes crosstalk-free control and quantum non-demolition (QND) readout of a large number of atomic qubits challenging. In this talk I will present our latest results of a dual-element atom array with individual control of single Rb and Cs atoms. We demonstrate independent placement of the elements in arrays with up to 512 trapping sites and observe negligible crosstalk. By continuously reloading one atomic element while maintaining an array of the other, we demonstrate a new continuous operation mode for atom arrays without any off-time. I will discuss avenues for ancilla-assisted quantum protocols such as QND measurements and quantum error correction, and present our recent progress. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D34.00004: Quantum Simulating Scalar Electrodynamics with Configurable Rydberg Atoms Arrays Yannick L Meurice, Jin Zhang, Shan-Wen Tsai, Alexander Keesling, James Corona, Fangli Liu, Shengtao Wang, Tout T Wang, Mikhail Lukin, Nathan Gemelke We present a quantum Hamiltonian for scalar electrodynamics in one and two spatial dimensions where the electric field Hilbert space is approximated by a spin-1 triplet. We propose two different quantum simulators for this model obtained by assembling arrays of Rydberg atoms with ladder structures. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D34.00005: Assembly and coherent control of a register of nuclear spin qubits - Part I Kayleigh A Cassella
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Monday, March 14, 2022 4:24PM - 4:36PM |
D34.00006: Assembly and coherent control of a register of nuclear spin qubits - Part II Eli Megidish Ultracold neutral atoms have emerged as a promising platform for scalable quantum computation. We are utilizing an optical tweezer platform for assembling and individually manipulating a two-dimensional register of nuclear spin qubits. Each nuclear spin qubit is encoded in the ground 1S0 manifold of 87Sr and is individually manipulated by site-selective addressing beams. In this talk I will present our progress in implementing high fidelity single and multiple qubit gates which are the essential building blocks for scalable quantum computation. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D34.00007: Noise Robustness Analysis and Process Tomography for Adiabatic Rydberg Gates Kaiwen Gui, Mark Saffman, Martin Lichtman Neutral atom arrays are some of the most promising quantum computing platforms due to their scalability and connectivity. However, similar to other platforms, multi-qubit gate imperfections present a major barrier to realizing practical quantum algorithms. Theoretical studies have shown the ability to realize highly accurate CZ gates with F ~ 0.9998 [1], well above the threshold of fault-tolerant quantum computing. However, recent experiments have only demonstrated CZ gates with F ~ 0.97 in 1D array [2] and F ~ 0.89[3] and 0.96[4] in 2D arrays. This work develops techniques that aim to improve the demonstrated fidelities and bridge the gap between theory and experiment. |
Monday, March 14, 2022 4:48PM - 5:00PM |
D34.00008: Stochastic Schrödinger equation derivation ofnon-Markovian two-time correlation functions Yusui Chen, Rafael Carballeira, Debing Zeng, David Dolgitzer, Peng Zhao We derive the evolution equations for two-time correlation functions of a generalized non-Markovian open quantum system based on a modified stochastic Schrödinger equation approach. We find that the two-time reduced propagator, an object that used to be characterized by two independent stochastic processes in the Hilbert space of the system, can be simplified and obtained by taking ensemble average over one single noise. This discovery can save the cost of computation, and accelerate the converging process when taking the average over noisy trajectories. As a result, our method can be widely applied to many open quantum models, especially large-scale systems, and extend the quantum regression theory to the non-Markovian case. In the short-time simulations, it is observed a significant difference between Markovian and non-Markovian cases, which can be applied to realize the environmental spectrum detection and enhance the measurement sensitivity in varying open quantum systems. |
Monday, March 14, 2022 5:00PM - 5:12PM |
D34.00009: Quantum phases in models of multi-leg ladders of Rydberg atoms Jin Zhang, Yannick L Meurice, Shan-Wen Tsai It has been demonstrated that Rydberg atoms trapped in arrays of optical tweezers are very effective simulators for quantum theories. We consider several configurations of arrays of Rydberg atoms, of which the effective Hamiltonians are spin-one models. We study the ground-state phase diagrams for these models, discuss the type of phase transitions, and explore the physics of the multicritical points in the phase diagrams. We comment on the relationship between the spin-one models and the truncated Abelian Higgs model, which indicates that the truncations of compact variables in the dual space can be responsible for very interesting phase transitions. |
Monday, March 14, 2022 5:12PM - 5:24PM |
D34.00010: Measurement-induced purification transition in a numerical free-fermion model Joseph W Merritt, Lukasz Fidkowski Quantum hybrid dynamics, involving unitary gates and projective measurements, have been shown in a wide array of cases to exhibit a measurement-induced purification transition. The “mixed” phases of such models take exponentially long to purify, and often have quantum error-correcting properties. We numerically study a case of hybrid dynamics in a specific fermion model. Motivated by a mapping to a statistical mechanics model, we study evolution by free-fermion gaussian unitary gates interspersed with projective measurements, and find evidence of such a phase transition. We plot the phase diagram, extract critical exponents for the transition, and compare the results to related models. |
Monday, March 14, 2022 5:24PM - 5:36PM |
D34.00011: Reducing the Sensitivity of Quantum Gates to Laser Intensity Noise via Real-Time Feedback on Gate Parameters Yonatan Cohen, Ramon Szmuk, Yoav Romach, Niv Drucker Quantum processors using laser fields to drive qubits suffer from laser intensity fluctuations which limit gate fidelities. Mitigation of such noise processes via feedback was up until now only available via low bandwidth sequencers running on CPUs (allowing at best for shot to shot corrections) or on FPGA processors and analog circuits that take orders of magnitude longer to develop and iterate on. In this talk, we demonstrate a novel hardware and software architecture allowing the generation of high bandwidth (>250kHz) feedback programs written in a Turing-complete, high-level programming language called QUA. The approach is based on the real-time synthesis of signals using QM’s pulse processor, a novel chip architecture and instruction set designed to generate quantum circuits. |
Monday, March 14, 2022 5:36PM - 5:48PM |
D34.00012: Entanglement, self-similarity and emergent quantum order in fractal lattice systems Wei Wang Motivated by recent experimental advances in realizing quantum matters with fractal geometry and in fractional dimension, we study the entanglement of many-qudit systems on fractal lattices and the quantum order emerging from thereon. In such systems, translational symmetry has no place while the fractal self-similarity shapes the scaling, hence indicating novel quantum phase of matter. We try to explore such novelty with Bose-Hubbard-type models whose ground states are entanglement-renormalization fixed points with long-range entanglement patterns. We show that a quantum-error-correction structure capturing the low-energy physics gives rise to the self-similar and long-range entanglement pattern, and portrays the emergent quantum order. We also show how numerical tools can be used to probe such novel quantum phases. |
Monday, March 14, 2022 5:48PM - 6:00PM |
D34.00013: Stellar representation of extremal Wigner-negative spin states Jack Davis, Robie Hennigar, Robert Mann, Shohini Ghose We use the Majorana stellar representation to characterize maximally nonclassical spin states with respect to the negative volume of the SU(2)-covariant Stratonovich-Wigner quasiprobability distribution. Comparisons are made to alternative definitions of nonclassicality, including anticoherence, the geometric measure of entanglement, and $P$-representability. Despite varying low-dimensional agreement between these definitions, the maximally Wigner-negative states are generally found to disagree with the others, with their higher order constellations not corresponding to a Platonic solid when available, or any other similar geometric embedding. We further find for spin systems with $j \leq \frac{7}{2}$ that random constellations/states are in general not particularly Wigner-negative relative to the maximum. Time permitting, we will also review our proof that all spin coherent states of arbitrary dimension are not positive-definite. |
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