Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B75: Quantum Simulation with Superconducting QubitsFocus
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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 Bose-Hubbard 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 many-body physics. I will present our recent work in constructing low-entropy quantum fluids of light by employing particle-resolved assembly combined with robust adiabatic preparation [1]. This experiment is performed in a 1D Bose-Hubbard 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 tunneling-induced quantum fluctuations. Site-resolved readout allows us to characterize these multi-particle fluids. Inter-site entanglement measurements reveal that the particles are delocalized, and two-body density correlation measurements demonstrated that they also avoid one another, revealing Friedel oscillations characteristic of a Tonks-Girardeau gas. Finally, I will describe our efforts in investigating out-of-equilibrium dynamics in this quantum system, by leveraging the precise time- and space-resolved control of the lattice potential landscape. We employ many-body 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 many-body states and observe the propagation of sound excitations of light in the lattice. Furthermore, we probe the many-body dynamics when incorporating integrability-breaking perturbations, to investigate the propagation of quantum entanglement and thermalization. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B75.00002: Many-body Ramsey as a Probe of Superfluid Compressibility in the Bose-Hubbard 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 many-body physics. We engineer a 1D Bose Hubbard chain using capacitively coupled transmon qubits, with individual qubit frequency tuning and single-site resolved readout. We deterministically prepare low-entropy fluid eigenstates of our system using particle-by-particle assembly and adiabatic tuning of disorder. This state preparation technique is reversible; combining it with a many-body 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 trade-off between robustness and tunability is a central challenge in the pursuit of quantum simulation and fault-tolerant 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 fixed-frequency 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 many-body 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 two-qubit 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 three-qubit CCZ gate with a fidelity of 96.18(5)\%. Importantly, the protocol is applicable to various fixed-frequency high-coherence platforms, thereby unlocking a suite of essential interactions for high-performance 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 trade-off between robustness and tunability in quantum devices is a central challenge in the pursuit of practical quantum advantage and fault-tolerant quantum computing. In particular, certain emerging solid-state 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 frequency-modifiable Floquet states, we demonstrate an XXZ Heisenberg interaction model with fully adjustable anisotropy between statically coupled fixed-frequency transmon circuits. Such an archetypal model allows quantum simulation of exotic many-body physics such as quantum phase transitions of spin systems, phantom spin-helix states, or formation of multi-photon bound states. To illustrate the robustness and versatility of the protocol, we tailor the transverse and longitudinal coupling independently, and implement two-qubit 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 three-qubit 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 solid-state platforms, thereby unlocking a suite of essential interactions for hardware-efficient quantum computing and simulation using fixed-frequency architectures. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B75.00005: Chiral coupling of a superconducting artificial atom to a 1-dimensional waveguide Frank Y Yang, Chaitali Joshi, Mohammad Mirhosseini Chiral light-matter 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 many-body 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 time-modulated 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 non-linear 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 light-matter 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 Many-Body 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 many-body systems. In so-called analog quantum simulations, a many-body 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 many-body correlation functions. For example, in one particular design, many-body anomalous correlation functions can be obtained from the spectral analysis of current in the read-out 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 Multi-qubit architectures in the superconducting platform mostly use coupled transmon devices. Recent studies have shown that these many-body coupled nonlinear oscillator systems display chaotic behaviour in certain regimes of the inter-qubit 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 inter-qubit 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 Landau-Zener 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 Landau-Zener model as a function of the Landau-Zener 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, Roman-Pascal Riwar Quantum circuit theory is a powerful and ever-evolving 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 offset-charge dispersion is believed to emerge due to a quantum circuit version of the Aharonov-Casher 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: 3-Qubit 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 high-energy physics. An important class of these simulations is lattice gauge theories (LGTs). LGT is a framework to study gauge theories in discretized space-time, 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 many-body 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 two-body interactions that, in general, break the conservation laws. In this talk, we propose and implement a parametrically activated 3-qubit 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 3-qubit interaction. |
Monday, March 6, 2023 1:54PM - 2:06PM |
B75.00011: Hamiltonian extrema of an arbitrary flux-biased Josephson circuit Alessandro Miano, Vidul R Joshi, Wei Dai, Gangqiang Liu, Pranav D Parakh, Luigi Frunzio, Michel H Devoret Flux-biased 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 non-linear superconducting circuit. In this talk, we present such method. It naturally captures the properties of single- and multi-minima 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, Roman-Pascal Riwar Superconductor–normal-metal–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.
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