Bulletin of the American Physical Society
2024 APS March Meeting
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session A51: Applications on Noisy Quantum Hardware IFocus

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Sponsoring Units: DQI Chair: Patrick Becker, University of Maryland, College Park Room: 200IJ 
Monday, March 4, 2024 8:00AM  8:36AM 
A51.00001: Quantum simulation of conical intersections using trapped ions. Invited Speaker: Jacob H Whitlow Conical intersections often control the reaction products of photochemical processes and occur when two electronic potential energy surfaces intersect [1]. Theory predicts that the conical intersection will result in a geometric phase for a wavepacket on the ground potential energy surface [2], and although conical intersections have been observed experimentally, the geometric phase has not been directly observed in a molecular system. In this presentation, I discuss results and methods from recent work [3] where we used a trapped atomic ion system to perform a quantum simulation of a conical intersection. The ion’s internal state served as the electronic state, and the motion of the atomic nuclei was encoded into the motion of the ions. The simulated electronic potential was constructed by applying statedependent optical forces to the ion. We experimentally observed a clear manifestation of the geometric phase using adiabatic state preparation followed by motional state measurement. 
Monday, March 4, 2024 8:36AM  8:48AM 
A51.00002: Highfidelity analog quantum simulation with superconducting qubits Trond I Andersen, Xiao Mi, Amir H Karamlou, Nikita Astrakhantsev, Andrey Klots, Julia Berndtsson, Andre Petukhov, Dmitry Abanin, Lev B Ioffe, Yu Chen, Vadim Smelyanskiy, Pedram Roushan Analog quantum simulation is a promising path for achieving beyondclassical simulation applications, particularly due to its faster entanglement growth than digital circuits. The higher classical simulation complexity in analog simulation is rooted in the simultaneous interaction between all qubits and the potential inclusion of noncomputational states in the Hilbert space; however, these same aspects also make analog calibration a daunting task. We here report on recent progress toward a transmonbased highfidelity analog quantum simulator. Specifically, we present a new analog calibration framework achieving significant reduction in eigenfrequency error compared to past works. We then demonstrate timedomain control of the analog quantum simulator via crossentropy benchmarking, and leverage hybrid digitalanalog circuits to study the equilibrium and nonequilibrium properties of the 2D XY model. Our work paves the way for analog quantum simulation to become a competitive avenue toward beyondclassical applications. 
Monday, March 4, 2024 8:48AM  9:00AM 
A51.00003: Experimental Realization of Topological Floquet Models in Circuit QED Martin A Ritter, David M Long, Ben Cochran, Ibukunoluwa A Adisa, Maya M Amouzegar, Anushya Chandran, Alicia J Kollar Topological band structures are well known to produce symmetryprotected chiral edge states which transport particles unidirectionally. These same effects can be harnessed in the frequency domain using a spin1/2 system subject to periodic drives [1]. Previously, the topological regime of such models was thought to be experimentally inaccessible due to a need for ultrastrong coupling; however, recent results have shown that the desired Hamiltonian is achievable in a rotating frame and can give rise to "boosting" of nonclassical states of light in a cavity [2]. We show that the rotating magnetic field required for boosting can be achieved by combining an oscillatory flux bias with an amplitude modulated microwave drive in quadrature. Field amplitudes exceeding 100 MHz in both the X and Z axes have been achieved, surpassing the intrinsic qubitcavity g of 30 MHz. The spatial profiles of the drive and boost cavities are used to design a low crosstalk chip with drive to boost isolation exceeding 40 dB. We present preliminary characterization of the cavity state boosting protocol. 
Monday, March 4, 2024 9:00AM  9:12AM 
A51.00004: Practical Quantum Simulations from Error Mitigation and Qubit Subspace Techniques Tim Weaving, Alexis P Ralli, Peter V Coveney, Peter J Love, William M Kirby, Andrew Tranter, Sauro Succi, Vinul Wimalaweera

Monday, March 4, 2024 9:12AM  9:24AM 
A51.00005: Observation of critical entanglement and quantum phase transitions on a quantum computer Qiang Miao, Thomas Barthel, Kenneth R Brown, Marko Cetina The simulation of stronglycorrelated quantum matter poses a significant challenge due to the curse of dimensionality and complex entanglement structures. This complexity is especially pronounced in the critical regime, where quantum fluctuations occur at all length scales and lowenergy states are highly entangled. The (Trotterized) multiscale entanglement renormalization ansatz  a special type of tensor networks with narrow causal cones  makes it possible to study large manybody systems on noisy intermediatescale quantum (NISQ) devices. Here we report on experimental results using iontrap systems. In particular, we demonstrate a quantum phase transition with spontaneous symmetry breaking in the thermodynamic limit and we measure bipartite entanglement entropies, which scale according to an area law for gapped systems and according to a logarea law at the critical point. The experimental demonstration of the (Trotterized) multiscale entanglement renormalization ansatz approach with preoptimized states is a pivotal step towards a fullfledged and practicable digital simulation of manybody systems on quantum computers. 
Monday, March 4, 2024 9:24AM  9:36AM 
A51.00006: Quantum Computed Green's Functions using a Cumulant Expansion of the Lanczos Method Gabriel GreeneDiniz, Kentaro Yamamoto, David Manrique, Evgeny Plekhanov, Rei Sakuma, Nathan Fitzpatrick In this work, we present a quantum computational method to calculate the manybody Green's function matrix in a spin orbital basis. We apply our approach to finitesized fermionic Hubbard models and related impurity models within Dynamical Mean Field Theory, and demonstrate the calculation of Green's functions on Quantinuum's H11 trappedion quantum computer. Our approach involves a cumulant expansion of the Lanczos method, using Hamiltonian moments as measurable expectation values. This bypasses the need for a large overhead in the number of measurements due to repeated applications of the variational quantum eigensolver (VQE), and instead measures the expectation value of the moments with one set of measurement circuits. From the measured moments, the tridiagonalised Hamiltonian matrix can be computed, which in turn yields the Green's function via continued fractions. While we use a variational algorithm to prepare the ground state in this work, we note that the modularity of our implementation allows for other (nonvariational) approaches to be used for the ground state. 
Monday, March 4, 2024 9:36AM  9:48AM 
A51.00007: Simulating Parity Magnetic Effects with Superconducting Qubits Yang Yu A highly tunable diamond energy diagram is constructed with four coupled superconducting qubits. We parametrically modulate their tunable couplers, mapping the momentum space to parameter space and realizing 4D Diraclike Hamiltonian with fourfold degenerate points. Then we apply an additional pump microwave field to manipulate the energy of tensor monopoles, providing an effective magnetic and pseudoelectric field. By using nonadiabatic response methods we obtain the fractional second Chern number. Combining these elements we obtain the topological current of parity magnetic effect. Our experiments pave the way to explore the higherdimensional topological states of matter and deepen our understanding of the topological effects. 
Monday, March 4, 2024 9:48AM  10:00AM 
A51.00008: Scattering in 1+1D Scalar Field Theory on a Quantum Computer Nikita A Zemlevskiy, Henry F Froland, Martin J Savage The scattering of wavepackets in onedimensional interacting scalar field theory is simulated on a quantum computer. To initialize the "asymptotic states" for the scattering, the vacuum of the theory is prepared with a variational algorithm. Localized wavepackets with equal but opposite momenta are then created on opposite ends of the lattice. The system is then timeevolved to study the dynamics of scattering events and their products. Quantum resource requirements and impacts of digitization and discretization on the quality of the results are discussed, as well as challenges and implications of this work. 
Monday, March 4, 2024 10:00AM  10:12AM 
A51.00009: Digital quantum simulation of thermal observables using a global quench Nikolay Gnezdilov, Hugo Perrin, Thibault Scoquart, Andrei Pavlov Thermal state preparation is essential for quantum simulation since it describes the natural equilibrium states of matter. We discuss the thermalization protocol based on a global quench that induces alltoall random interaction within a fewqubit system. The interaction constants are drawn from complex Gaussian distribution. Running the protocol multiple times and averaging the results over realizations of the interaction constants leads to thermal observables. We implement our protocol on the IBM quantum computer for a fourqubit system. Using circuit recompilation, we restore the thermal observables predicted by the exact dynamics evaluated on a classical computer. We show thermal occupation probabilities for the sixteen states with temperature controlled by the variance of the interaction constants and duration of the quench protocol. 
Monday, March 4, 2024 10:12AM  10:24AM 
A51.00010: Quantum dynamics of a twolevel fractional Hall system on NISQ devices. Ammar Kirmani, Benedikt Fauseweh, Jianxin Zhu In quantum fractional Hall systems, physical properties are dominated by electronelectron interaction, resulting in most remarkable phenomenon like quantized resistivity, fractional quasiparticle excitations etc. Ground state properties and excited state dynamics of such systems can be evaluated on classical computer using exact diagonalization techniques on small systems due to an exponential increase of the Hilbert space. In this talk, we will present quantum algorithms to simulate shorttime quantum dynamics of a twolevel fractional Hall system under a laserdriven electromagnetic pulse. By using IBMNISQ Quantum Computers, we identify the existence of highly novel excited states that carry Hall current. In addition, high harmonic generation of such nontrivial phenomena is also measured on quantum computers.

Monday, March 4, 2024 10:24AM  10:36AM 
A51.00011: Nonlocal quantum games using deformed topologically ordered states Oliver Hart, David T Stephen, Dominic J Williamson, Michael FossFeig, Rahul Nandkishore We introduce a nonlocal quantum game for which toric code ground states are a resource. Players who share a fixedpoint state beforehand win with unit probability, whereas the optimal classical strategy only wins three quarters of the time. Unlike previous examples, the fixedpoint strategy continues to surpass the optimal classical strategy away from the fixed point, leading to robust quantum advantage throughout an appreciable fraction of the toric code phase. We demonstrate this robustness experimentally on the Quantinuum H11 quantum computer by playing the game with a continuous family of randomly deformed toric code states created by applying weak measurements to every qubit. 
Monday, March 4, 2024 10:36AM  10:48AM 
A51.00012: Quantum simulation of scalar field theories in qudit systems Doga M Kurkcuoglu, Sohaib Alam, Joshua A Job, Andy C. Y. Li, Alexandru Macridin, Gabriel N Perdue, Stephen Providence We discuss the implementation of quantum algorithms for lattice Φ4 theory on circuit quantum electrodynamics (cQED) system. The field is represented on qudits in a discretized field amplitude basis. The main advantage of qudit systems is that its multilevel characteristic allows the field interaction to be implemented only with diagonal singlequdit gates. Considering the set of universal gates formed by the singlequdit phase gate and the displacement gate, we address initial state preparation and singlequdit gate synthesis with variational methods. 
Monday, March 4, 2024 10:48AM  11:00AM 
A51.00013: Probing correlated phase of quantum matter in drivendissipative superconducting circuit lattice Botao Du, Qihao Guo, Ramya Suresh, Santiago Lopez, Ruichao Ma Superconducting (SC) circuits have recently emerged as one of the leading platforms for quantum computation and simulation. Utilizing the high flexibility of the circuit QED toolbox, engineered baths offer a new powerful tool for the drivendissipative control of quantum states and quantum processes. In this work, we create bathcoupled SC circuit analog quantum simulators to explore manybody physics in open quantum systems. We implement a hardwareefficient way to engineer dynamically tunable local particle baths by controlling the sideband coupling between the SC lattice and readout resonators, and apply them to prepare manybody states in a circuit BoseHubbard lattice. We present a new method for measuring current and current statistics in a strongly interacting lattice to characterize correlated lattice phases in open quantum systems. We will also discuss future plans for creating nonlocal correlated baths and their applications. 
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