Bulletin of the American Physical Society
2024 APS March Meeting
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session F54: Quantum Information Science in AMO PhysicsFocus

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Sponsoring Units: DAMOP Chair: Daniel Slichter, National Institute of Standards and Technology Boulder Room: 203AB 
Tuesday, March 5, 2024 8:00AM  8:36AM 
F54.00001: Quantum Simulation of manybody physics with accuracy guarantees Invited Speaker: Rahul Trivedi Several quantum hardware platforms, while being unable to perform fully faulttolerant quantum computation, can still be operated as analogue quantum simulators for addressing manybody problems. However, due to the presence of errors and without explicit error correction, both (a) the extent to which the output of the quantum simulator can be trusted, and (b) if the quantum simulators provide a computational advantage over classical algorithms, remain unclear. 
Tuesday, March 5, 2024 8:36AM  8:48AM 
F54.00002: Probing Su–Schrieffer–Heegerlike behavior in a tilted synthetic flux ladder Tianrui Xu, Ana Maria Rey, Anjun Chu Tilted optical lattice systems have been widely used in both quantum metrology and quantum simulations. In recent years, progress has been made to combine tilted optical lattices with optical lattice clocks using fermionic alkalineearth atoms (AEAs), resulting in a new platform with pristine quantum coherence and exquisite quantum control. In addition, the fermionic AEAs, with their n internal levels, have unique SU(n) symmetric collisions. This platform offers new capabilities to simulate and understand spinorbitcoupled, interacting manybody fermionic systems. In this talk, I discuss our theoretical studies of quantum dynamics of twolevel fermionic atoms in a tilted synthetic flux ladder, where we see a nontrivial interplay of the tilt, the nearestneighbor hopping and the spinorbitcoupled laser drives. In a specific parameter regime, accessible under current conditions, we can simulate a tilted Su–Schrieffer–Heeger (SSH) model with tunable inter and intracell couplings without the need of an additional superlattice potential. The topologically trivial and nontrivial phases of the untilted SSH model manifest on the longtime dynamics of chiral Bloch oscillations, which can be accessed via Ramsey spectroscopy. Our work paves the way to understand dynamics in tilted, multilevel quantum manybody systems. 
Tuesday, March 5, 2024 8:48AM  9:00AM 
F54.00003: Oral: Optimizing quantum logic spectroscopy for molecular state control Anastasia Pipi, Xuecheng Tao, David Leibrandt, Prineha Narang Quantum logic spectroscopy (QLS) is a powerful technique for precision measurements, enabling the control and nondestructive detection of molecular ion states that are challenging to manipulate otherwise[1]. While experimentally demonstrated, this method is limited by blackbody radiation exciting numerous hyperfine states, requiring a large number of measurements for state preparation and spectroscopic data collection. To address this challenge, we perform Monte Carlo simulations of a new protocol involving a twostep process. First, we couple at most half the total number of rotational states to a chosen normal mode shared between the molecular and logic ions, followed by a projective measurement of their motional state. By consistently repeating these two steps, we can gradually reduce the large state space to a single pure quantum state. The process is optimized to account for degeneracies and offresonant couplings by observing the dynamics through the transition matrix of the Markovian state model, which encodes information about how external laser pulses affect the probability distribution of the molecular state space. Additionally, the study explores the application of optimal control theory in designing robust laser pulses. This protocol reduces the number of measurements from linear to logarithmic scaling, improving our ability to manipulate molecular states and potentially observe parity violation signatures in molecules[2], or facilitate transduction between trapped ion qubits and photons[3]. 
Tuesday, March 5, 2024 9:00AM  9:12AM 
F54.00004: Molecular Entanglement Witness by Absorption Spectroscopy in Polariton Chemistry Weijun Wu, Francesca Fassioli Olsen, Gregory D Scholes Maintaining molecular entanglement at room temperature and detecting multipartite entanglement features of macroscopic molecular systems remain key challenges for understanding the nontrivial quantum effect in chemical quantum dynamics. Here, we study the quantum Fisher information, a central concept in quantum metrology, as a multipartite entanglement witness. We generalize the entanglement witness functional related to quantum Fisher information regarding nonidentical local response operators and show that it is a good molecular entanglement witness for ultrastrong lightmatter coupling in cavity quantum electrodynamics and even a multimolecular entanglement witness during the superradiance phase transition. We further connect quantum Fisher information to the dipole correlator, which suggests that molecular entanglement could be detected by linear absorption spectrum at finite temperatures. Our work proposes a general protocol to sufficiently measure molecular entanglement for chemical systems at room temperature in experiments and demonstrate the longlived multimolecular entanglement in the polariton chemistry systems. 
Tuesday, March 5, 2024 9:12AM  9:24AM 
F54.00005: Building graph states with optically trapped molecules Ryan Scott, Svetlana Kotochigova, Bryce Gadway, Brian L DeMarco, Vito W Scarola Molecular quantum systems offer a promising architecture for measurementbased quantum computing. These systems are highly controllable, optically addressable, and typically admit a natural twoparticle dipoledipole interaction. In this talk, we will discuss how to use molecular rotational levels of optically trapped bialkali systems to build graph states via the dipoledipole interaction under Floquet dressing. We will demonstrate the scalability of our results. Additionally, we will discuss possible generalizations from two and threelevel systems to greater numbers of rotational levels, as well as more complex states such as multigraph and hypergraph states. 
Tuesday, March 5, 2024 9:24AM  9:36AM 
F54.00006: Numerical study of entangled helical spin currents in a spinor BoseEinstein condensate Emi Yukawa We numerically study the dynamics of perfectly helical spin currents where two counterpropagating spin currents are quantummechanically entangled. A spin1 condensate is initially prepared at the m = 0 magnetic sublevel in a onedimensional torus. The atoms are assumed to interact via the swave scattering channel which parametrically generates an entangled pair of m = 1 and 1 atoms from two m = 0 atoms. The pair of m = 1 and 1 atoms acquire oppositely directed momenta via the Bragg diffraction, while they maintain the quantummechanical spin correlations. As a result, a nonzero spin current flows in the torus with no net mass current. 
Tuesday, March 5, 2024 9:36AM  9:48AM 
F54.00007: SuperExponential Scrambing and Slow Entanglement Growth in the Deep Hilbert Space of AlltoAll Systems Zihao Qi, Thomas Scaffidi, Xiangyu Cao Quantum dynamics of spin systems with uniform alltoall interactions have often been studied in the totally symmetric space (TSS) of maximal total spin. However, the TSS states are atypical in the full manybody Hilbert space. We explore several aspects of the alltoall quantum dynamics away from the TSS, and reveal surprising features of the "deep Hilbert space'' (DHS). We study the outoftime order correlator (OTOC) in the infinitetemperature ensemble of the full Hilbert space and show that the OTOC can grow superexponentially in the largeN limit, due to the fast dynamics in an unbounded phase space. By a similar mechanism, the Krylov complexity grows explosively. We also study the entanglement growth in a quantum quench from a DHS product state, i.e., one of nonaligned spins that resemble the DHS infinitetemperature ensemble with respect to the statistics of the collective spins. Using a fieldtheoretical method, We exactly calculate the entanglement entropy in the largeN limit. We show that, unlike in TSS, fast OTOC growth does not imply fast entanglement growth in the DHS. 
Tuesday, March 5, 2024 9:48AM  10:00AM 
F54.00008: Quantum coherence controls the nature of equilibration and thermalization in coupled chaotic systems Jethin Pulikkottil Jacob, Arul Lakshminarayan, Shashi C. L. Srivastava, Maximilian F. I. Kieler, Arnd Bäcker, Steven Tomsovic A bipartite system whose subsystems are fully quantum chaotic and coupled by a perturbative interaction with a tunable strength is a paradigmatic model for investigating how isolated quantum systems relax toward an equilibrium. It is found that quantum coherence of the initial product states in the energy eigenbasis of the subsystems—quantified by the offdiagonal elements of the subsystem density matrices—can be viewed as a resource for equilibration and thermalization as manifested by the entanglement generated. Results are given for four distinct perturbation strength regimes, the ultraweak, weak, intermediate, and strong regimes. For each, three types of tensor product states are considered for the initial state: uniform superpositions, random superpositions, and individual subsystem eigenstates. A universal timescale is identified involving the interaction strength parameter. In particular, maximally coherent initial product states (a form of uniform superpositions) thermalize under time evolution for any perturbation strength in spite of the fact that in the ultraweak perturbative regime the underlying eigenstates of the system have a tensor product structure and are not at all thermallike; though the time taken to thermalize tends to infinity as the interaction vanishes. Moreover, it is shown that in the ultraweak regime the initial entanglement growth of the system whose initial states are maximally coherent is quadraticintime, in contrast to the widely observed linear behavior. 
Tuesday, March 5, 2024 10:00AM  10:12AM 
F54.00009: Efficient Local Classical Shadow Tomography with Number Conservation Sumner Hearth, Anushya Chandran, Michael Flynn, Christopher R Laumann Quantum state tomography aims to produce a complete classical description of the state of a quantum system: a prohibitive task requiring exponential resources. Recent works have taken a different approach. They build an efficient classical description of the state, the socalled classical shadow, that can accurately capture properties of interest such as fewbody observables, but is a poor approximation to the entire density matrix. The protocol is simple to implement and predicts observables much more efficiently and accurately than other techniques. It has accordingly developed into an important experimental tool. 
Tuesday, March 5, 2024 10:12AM  10:24AM 
F54.00010: Spectra and phase transition in Grover's algorithm with systematic noise Sasanka Dowarah, Chuanwei Zhang, Vedika Khemani, Michael Kolodrubetz In this work, we present a study of Grover's search algorithm in the presence of systematic noise. By modeling the Grover operator within one timestep as a Floquet unitary, we showed that the bulk quasienergy spectrum is wellcaptured by the firstorder perturbation theory. Using the random matrix theory of an effective Hamiltonian, we obtain the scaling of the critical disorder for the algorithm. In addition, we also derive semianalytical results for the oscillation frequency of the target state in the presence of noise. 
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