Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 510)
Virtual (March 2022); Time Zone: Pacific Time
Session B75: Quantum Simulation with Superconducting QubitsFocus

Hide Abstracts 
Sponsoring Units: DQI Chair: Chris Wang, University of Chicago Room: Room 401/402 
Monday, March 6, 2023 11:30AM  12:06PM 
B75.00001: Strongly correlated fluids of light in a BoseHubbard circuit Invited Speaker: Andrei Vrajitoarea Manipulating quantum systems composed of interacting particles represents a central challenge of modern quantum science, with applications from quantum computation to manybody physics. I will present our recent work in constructing lowentropy quantum fluids of light by employing particleresolved assembly combined with robust adiabatic preparation [1]. This experiment is performed in a 1D BoseHubbard circuit implemented with an array of capacitively coupled transmon qubits. We leverage strong lattice disorder to inject individual photons into known localized eigenstates, then adiabatically remove this disorder to melt the photons into a fluid via tunnelinginduced quantum fluctuations. Siteresolved readout allows us to characterize these multiparticle fluids. Intersite entanglement measurements reveal that the particles are delocalized, and twobody density correlation measurements demonstrated that they also avoid one another, revealing Friedel oscillations characteristic of a TonksGirardeau gas. Finally, I will describe our efforts in investigating outofequilibrium dynamics in this quantum system, by leveraging the precise time and spaceresolved control of the lattice potential landscape. We employ manybody spectroscopic techniques to probe the quasiparticle excitations of the fluid, using perturbations in the lattice potential. These controlled perturbations can be applied coherently in our favor, allowing us to prepare superpositions of manybody states and observe the propagation of sound excitations of light in the lattice. Furthermore, we probe the manybody dynamics when incorporating integrabilitybreaking perturbations, to investigate the propagation of quantum entanglement and thermalization. 
Monday, March 6, 2023 12:06PM  12:18PM 
B75.00002: Manybody Ramsey as a Probe of Superfluid Compressibility in the BoseHubbard Circuit Gabrielle Roberts, Andrei Vrajitoarea, Brendan Saxberg, Margaret G Panetta, Jonathan Simon, David Schuster Superconducting circuits are an ideal platform for applying the tools of quantum computing to experiments probing manybody physics. We engineer a 1D Bose Hubbard chain using capacitively coupled transmon qubits, with individual qubit frequency tuning and singlesite resolved readout. We deterministically prepare lowentropy fluid eigenstates of our system using particlebyparticle assembly and adiabatic tuning of disorder. This state preparation technique is reversible; combining it with a manybody Ramsey experiment, we prepare cat states of quantum fluids, and then localize the information about energy differences of these highly entangled and delocalized states into one qubit for measurement. We then use this manybody Ramsey as a probe of adiabaticity and compressibility of the fluids at different system sizes and particle numbers. 
Monday, March 6, 2023 12:18PM  12:30PM 
B75.00003: Programmable Heisenberg interactions between Floquet qubits: Part 2 Yosep Kim, Long B Nguyen, Akel Hashim, Noah Goss, Brian Marinelli, Bibek Bhandari, Debmalya Das, Ravi K Naik, John Mark Kreikebaum, Andrew N Jordan, David I Santiago, Irfan Siddiqi The fundamental tradeoff between robustness and tunability is a central challenge in the pursuit of quantum simulation and faulttolerant quantum computation. In particular, many emerging quantum architectures are designed to achieve high coherence at the expense of having fixed spectra and consequently limited types of controllable interactions. Here, by adiabatically transforming fixedfrequency superconducting circuits into modifiable Floquet qubits, we demonstrate an XXZ Heisenberg interaction with fully adjustable anisotropy. This interaction model is on one hand the basis for manybody quantum simulation of spin systems, and on the other hand the primitive for an expressive quantum gate set. To illustrate the robustness and versatility of the Floquet protocol, we tailor the Heisenberg Hamiltonian and implement twoqubit iSWAP, CZ, and SWAP gates with estimated fidelities of 99.32(3)%, 99.72(2)%, and 98.93(5)\%, respectively. In addition, we implement a Heisenberg interaction between higher energy levels and employ it to construct a threequbit CCZ gate with a fidelity of 96.18(5)\%. Importantly, the protocol is applicable to various fixedfrequency highcoherence platforms, thereby unlocking a suite of essential interactions for highperformance quantum information processing using these architectures. From a broader perspective, our work provides compelling avenues for future exploration of quantum electrodynamics and optimal control using the Floquet framework. 
Monday, March 6, 2023 12:30PM  12:42PM 
B75.00004: Programmable Heisenberg interactions between Floquet qubits Long B Nguyen, Yosep Kim, Akel Hashim, Noah Goss, Brian Marinelli, Bibek Bhandari, Debmalya Das, Ravi K Naik, John Mark Kreikebaum, Andrew N Jordan, David I Santiago, Irfan Siddiqi The fundamental tradeoff between robustness and tunability in quantum devices is a central challenge in the pursuit of practical quantum advantage and faulttolerant quantum computing. In particular, certain emerging solidstate quantum architectures are designed to achieve high coherence at the expense of having invariable spectral configurations, thus limiting the range of native interactions between the qubits. Here, by encoding computational information onto frequencymodifiable Floquet states, we demonstrate an XXZ Heisenberg interaction model with fully adjustable anisotropy between statically coupled fixedfrequency transmon circuits. Such an archetypal model allows quantum simulation of exotic manybody physics such as quantum phase transitions of spin systems, phantom spinhelix states, or formation of multiphoton bound states. To illustrate the robustness and versatility of the protocol, we tailor the transverse and longitudinal coupling independently, and implement twoqubit iSWAP, CZ, and SWAP gates with estimated fidelities of 99.32(3)%, 99.72(2)%, and 98.93(5)%, respectively. In addition, by realizing the transverse coupling between higher levels leading to a threequbit CCZ gate with an estimated fidelity of 96.18(5)%, we show that the interactions can be generally engineered for multilevel systems without additional hardware components. Our Floquet protocol is broadly applicable to various solidstate platforms, thereby unlocking a suite of essential interactions for hardwareefficient quantum computing and simulation using fixedfrequency architectures. 
Monday, March 6, 2023 12:42PM  12:54PM 
B75.00005: Chiral coupling of a superconducting artificial atom to a 1dimensional waveguide Frank Y Yang, Chaitali Joshi, Mohammad Mirhosseini Chiral lightmatter interaction, wherein the coupling between atoms and photons depends on the propagation direction of light, enables a host of opportunities in quantum science. Unidirectional coupling of multiple atoms to a photonic bath produces a cascaded quantum system, with applications in deterministic state transfer, gate operations with itinerant photons, and study of quantum manybody physics. Here, we report on the realization of a superconducting artificial atom with unidirectional strong coupling to a waveguide. Our system operates in the giant atom regime of waveguide QED; it contains a transmon qubit with timemodulated couplings to two points of a microwave coplanar waveguide. Chirality is achieved by tailoring interference between these radiation pathways. In our device, coupling to forward propagating modes exceeds backward coupling by approximately two orders of magnitude. To demonstrate the quantum nonlinear response of our system, we perform resonance fluorescence measurements on the chiral atom, observing Mollow triplets under a strong resonant drive. Further, we show that the chiral behavior can be extended to the higher energy levels of the transmon qubit, opening up a range of rich possibilities for engineering unidirectional lightmatter gate operations or quantum state transfer. In the future, our device may serve as a fundamental building block for realizing cascaded quantum systems without the need for bulky, lossy circulators. 
Monday, March 6, 2023 12:54PM  1:06PM 
B75.00006: Probing ManyBody Correlations in Superconducting Circuits Kamal Sharma, Wade DeGottardi The quest to build quantum computers using superconducting circuits has led to tremendous advances in fabrication capabilities. These circuits are increasingly being used for other applications, notably the realization of engineered quantum manybody systems. In socalled analog quantum simulations, a manybody Hamiltonian is realized through specific couplings in the circuit. A challenge in this approach is identifying the states being realized in these open quantum systems. In this talk, I will describe superconducting circuit designs capable of accessing manybody correlation functions. For example, in one particular design, manybody anomalous correlation functions can be obtained from the spectral analysis of current in the readout circuit. Such measurements can pinpoint photon pair correlations. 
Monday, March 6, 2023 1:06PM  1:18PM 
B75.00007: Effect of chaos on gate fidelity in coupled transmon systems Sanket Tripathy, Baladitya Suri Multiqubit architectures in the superconducting platform mostly use coupled transmon devices. Recent studies have shown that these manybody coupled nonlinear oscillator systems display chaotic behaviour in certain regimes of the interqubit coupling strength. In this work, we characterize the dynamical effects of chaos on the quantum gates applied to the transmons. We apply OTOCs as a possible measure of chaos in a system of 1D transmon chains and compare it to spectral statistics used in earlier works. Further, we construct a model for practical gate implementation in this system, and through numerical simulations explore the effect of chaos on the gate fidelity while varying the interqubit coupling strength, local Hilbert space dimension and gate support. Finally, we compare our numerical calculations with analytical calculations to explain the results. 
Monday, March 6, 2023 1:18PM  1:30PM 
B75.00008: Quantum emulation of the transient dynamics in the multistate LandauZener model Martin P Weides, Alexander Stehli, Jan D Brehm, Tim Wolz, Andre Schneider, Alexey V Ustinov, Hannes Rotzinger Quantum simulation is one of the most promising near term applications of quantum computing. Especially, systems with a large Hilbert space are hard to solve for classical computers and thus ideal targets for a simulation with quantum hardware. In this work, we study experimentally the transient dynamics in the multistate LandauZener model as a function of the LandauZener velocity. The underlying Hamiltonian is emulated by superconducting quantum circuit, where a tunable transmon qubit is coupled to a bosonic mode ensemble comprising 
Monday, March 6, 2023 1:30PM  1:42PM 
B75.00009: Compact description of quantum phase slips and the fate of the Aharonov–Casher effect Christina Koliofoti, RomanPascal Riwar Quantum circuit theory is a powerful and everevolving tool to predict the dynamics of superconducting circuits. In its language, quantum phase slips (QPSs) are famously considered to be the exact dual to the Josephson effect. We argue that this duality suffers from issues with the topology and the size of the Hilbert space, and is incompatible with charge quantization. We provide a treatment with a reduced, compactified Hilbert space, which changes the predictions of various quantum circuits. In this talk we focus in particular on circuits with multiple QPS junctions, where the observed offsetcharge dispersion is believed to emerge due to a quantum circuit version of the AharonovCasher effect: a coherent interference between phase slips occurring on neighbouring junctions. By means of our compact theory, we reassess the physics of such circuits, and find to the contrary that these oscillations emerge from the compactness of the phase variable. Moreover, we show that our theory does not provide a regime where the offset charge dependence can be reduced to a simple interference pattern of quantum phase slip amplitudes. Our theory thus provides both a significant qualitative and quantitative revision of QPS physics. 
Monday, March 6, 2023 1:42PM  1:54PM Author not Attending 
B75.00010: 3Qubit parametric interaction as a tool for quantum simulation Jamal H Busnaina, Cindy Yang, Ibrahim Nsanzineza, Christopher Wilson Until universal quantum computers become capable of simulating complicated quantum systems, analog quantum simulators offer the potential to take significant steps in tackling numerous classically intractable problems in areas such as condensed matter physics, chemistry, and highenergy physics. An important class of these simulations is lattice gauge theories (LGTs). LGT is a framework to study gauge theories in discretized spacetime, often employed when perturbative techniques fail. The eponymous gauge symmetries present in these theories lead to conservation laws, generalizations of Gauss's Law in electrodynamics, that relate the configuration of "matter" sites to the configuration of gauge fields. Any simulation of a gauge theory must ultimately reproduce these conservation laws, with one strategy in analog simulation being to build them in at the hardware level. This strategy requires having manybody interactions between the elements representing the matter and gauge fields, such that their configurations can evolve simultaneously. At that same time, we must suppress standard twobody interactions that, in general, break the conservation laws. In this talk, we propose and implement a parametrically activated 3qubit interaction in a circuit QED architecture, as the simplest building block for simulating LGTs in a superconducting photonic lattice. We will discuss the device design and demonstrate the experimental realization of the 3qubit interaction. 
Monday, March 6, 2023 1:54PM  2:06PM 
B75.00011: Hamiltonian extrema of an arbitrary fluxbiased Josephson circuit Alessandro Miano, Vidul R Joshi, Wei Dai, Gangqiang Liu, Pranav D Parakh, Luigi Frunzio, Michel H Devoret Fluxbiased loops hosting one or more Josephson junctions are ubiquitous elements in quantum information processing based on superconducting hardware. These circuits can be tuned to implement a variety of Hamiltonians, with applications ranging from advanced qubits to quantum limited converters and amplifiers. In particular, the Hamiltonian extrema of these superconducting loops are of special interest for understanding their local and global properties. However, the theory of superconducting quantum circuits still lacks a systematic method to compute the series expansion of the Hamiltonian around these extrema for an arbitrary nonlinear superconducting circuit. In this talk, we present such method. It naturally captures the properties of single and multiminima Hamiltonians and can be generalized to networks consisting of multiple loops. With the steady advance of design and fabrication techniques of quantum processors, this approach can facilitate the advent of the next generations of superconducting quantum circuits with enhanced functionalities. 
Monday, March 6, 2023 2:06PM  2:18PM 
B75.00012: Generalising Beenakker Equation to Take into Account Evanescent Modes Daniel Kruti, RomanPascal Riwar Superconductor–normalmetal–superconductor Josephson junctions have been examined extensively in past years. In particular, the case where the normal region is modelled by an ideal normal conductor with an intermittent scattering region can be well described by the celebrated Beenakker equation. Strictly speaking however, this equation is applicable only in the asymptotic plain wave limit, neglecting evanescent modes. However, the situation is changing by recent experimental advances. First, conductor regions are now fabricated with significantly decreased impurity scattering, leading to situations where scattering is dominated by the junction geometry. Second, miniaturisation is advancing such that evanescent modes should no longer be neglected. While this regime has already been captured by numerical methods, we here present an explicit analytical treatment, and generalise the Beenakker equation to short junctions with evanescent modes and geometric scattering in order to investigate the structure of Andreev bound states.

Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2024 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700