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 A75: Superconducting qubit circuit theoryFocus
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Sponsoring Units: DQI Chair: Adrian Parra Rodriguez, Université de Sherbrooke Room: Room 401/402 |
Monday, March 6, 2023 8:00AM - 8:36AM |
A75.00001: Exact Solutions of Interacting Dissipative Systems via Weak Symmetries Invited Speaker: Alexander McDonald As superconducting qubit-based quantum information processors continue to improve, a better understanding of strongly-interacting dissipative quantum models is required to accurately model such systems. Exact solutions in such instances however are few and far between; adding dissipation to even the simplest closed-system Hamiltonian often means resorting to numerics or employing unjustified approximations. |
Monday, March 6, 2023 8:36AM - 8:48AM |
A75.00002: Generalized time-coarse graining as a systematic perturbation theory beyond RWA I: An introduction and computational framework Leon Y Bello, Wentao Fan, Aditya Gadontra, Hakan E Tureci The rotating-wave approximation neglects the rapidly-oscillating (counter-rotating) terms in the Hamiltonian, assuming the effects average off over the relevant time-scales. However, these terms often yield non-negligible corrections to the dynamics, and one must go beyond that approximation. Specifically, they can become quite important in the study of parametric couplers and amplifiers, where accurate modeling of the system is critical for achieving high-fidelity operation. |
Monday, March 6, 2023 8:48AM - 9:00AM |
A75.00003: Generalized time-coarse graining as a systematic perturbation theory beyond RWA II: Application to drive-induced qubit transitions in transmons and fluxoniums Wentao Fan, Leon Y Bello, Hakan E Tureci In order to achieve rapid dispersive readout for artificial atoms in circuit QED, a strong drive can be applied to a readout resonator coupled to the atoms. However, for both transmons and fluxoniums, dispersive coupling to a strongly driven resonator may not only significantly increase the qubit relaxation rate, but also induce spurious excitations outside the computational space, even if the drive frequency is far off-resonance from any atom transition frequencies. In this talk, we present effective time-coarse grained models for transmons and fluxoniums, and derive analytical formulas for the drive-induced transition rates as well as the Purcell decay rate. We also study backreaction from the atom to the resonator, and demonstrate that it is responsible for induced resonator nonlinearity and deviations from coherent steady states. |
Monday, March 6, 2023 9:00AM - 9:12AM |
A75.00004: Modeling the effects of quantum non-Markovian noise in strongly driven quantum systems Peter Groszkowski, Alireza Seif, Jens Koch, Aashish A Clerk Driven quantum systems subject to non-Markovian noise are typically difficult to model accurately. Recently [1], we presented a systematic method based on a generalized cumulant expansion for deriving pseudo-Lindblad Master equations (PLMEs) that can accurately capture the effects of classical, highly correlated noise. PLMEs are equations of motion that parallel the standard Lindblad form, however, allow for the jump rates to be negative. In this talk, we expand on our previous efforts, and show how to treat noise that is not just highly correlated, but also quantum. Using techniques based on Floquet theory, we also discuss how to capture the effects of strong coherent driving, that were previously not discussed. Through numerical simulations, we show that our effective description of the system evolution can often lead to a more accurate prediction of its dynamics than can be achieved by commonly utilized phoenomenological approaches. |
Monday, March 6, 2023 9:12AM - 9:24AM |
A75.00005: Non-Markovian noise affecting superconductng circuits Balázs Gulácsi, Guido Burkard Electrical circuits containing superconducting elements are one of the leading platforms for building an efficiently working quantum processor. Like any other realistic quantum system, superconducting qubits are open quantum systems, and the deleterious effects of their environment are the major obstacle on the road for reaching fault-tolerant quantum computation. In our work, we describe temporally correlated noise processes, that influence the idle evolution of a superconducting qubit. We model the composite qubit-environment system using quantum circuit theory, and we show how a circuit Hamiltonian can be derived for both longitudinal and transverse noise affecting the qubit. Based on the time-convolutionless projection operator method, we construct a master equation that is capable of capturing non-Markovian behaviour of the reduced system dynamics. By expressing the solution of the master equation in the Kraus representation, we are able to predict non-Markovian phenomena such as revivals of coherence, and also identify the limits of our theory by checking whether complete positivity is respected. |
Monday, March 6, 2023 9:24AM - 9:36AM |
A75.00006: Floquet theory for bichromatic driving in single and two-qubit quantum gates Bibek Bhandari, Debmalya Das, Long B Nguyen, Yosep Kim, Andrew N Jordan We study the dynamics of a single and coupled superconducting qubit system driven by bichromatic pulses. Using the Floquet theory framework, we investigate weak and strong driving regimes. It has been observed that bichromatic driving can be applied to suppress unwanted nonadiabatic transitions in single and two-qubit gates using shortcuts to adiabaticity technique. Moreover, the unwanted ZZ crosstalk can be mitigated in two-qubit gates by driving the two qubits with a phase. Motivated by the aforementioned observations, we utilize Floquet theory and shortcuts to adiabaticity techniques to obtain fast and high-fidelity one and two-qubit quantum gates based on superconducting qubits. We also numerically and analytically study the multiphoton resonance processes and quantum interference phenomena for the bichromatically driven single and two-qubit system. |
Monday, March 6, 2023 9:36AM - 9:48AM |
A75.00007: Experimental demonstration of the treatment of time-dependent flux in circuit QED devices Jacob Bryon, Daniel K Weiss, Xinyuan You, Sara F Sussman, Xanthe Croot, Ziwen Huang, Jens Koch, Andrew A Houck The choice of allocation of external flux to inductive elements in circuit quantum-electrodynamics was long thought to be arbitrary, until recent theoretical work emphasized that this is not the case [1]. Without careful consideration there often arises an additional term in the time-dependent Hamiltonian proportional to $dPhi/dt$. Here we present an experimental demonstration of this theory using a fluxonium qubit and investigating the effects of fast flux ramps. Our data is consistent with theory which includes the additional time derivative term, validating the treatment of time-dependent flux in circuit quantization presented in [1]. |
Monday, March 6, 2023 9:48AM - 10:00AM |
A75.00008: Algebraic canonical quantization of lumped superconducting networks Adrian Parra Rodriguez, Iñigo L Egusquiza We present a systematic canonical quantization procedure for lumped-element superconducting networks [1,2,3] by using a redundant configuration-space description. The algorithm is based on an original, explicit, and constructive implementation of the symplectic diagonalization of positive semidefinite Hamiltonian matrices, a particular instance of Williamson's theorem [4,5]. With it, we derive canonically quantized discrete-variable descriptions of passive causal systems. We exemplify the algorithm with representative singular electrical networks, a nonreciprocal extension for the black-box quantization method, as well as an archetypal Landau quantization problem. This viewpoint can be enriched using the techniques of quantization of constraint systems [5]. |
Monday, March 6, 2023 10:00AM - 10:12AM |
A75.00009: Dirac physics and charge localization due to quasiperiodic nonlinear capacitances Tobias Herrig, Jedediah H Pixley, Elio J König, Roman-Pascal Riwar Superconducting circuits are an extremely versatile platform to realize quantum information hardware, and, as was recently realized, to emulate topological materials, such as Weyl semimetals or Chern insulators. We here show how a simple arrangement of capacitors and conventional SIS junctions can realize a nonlinear capacitive element with a surprising property: it can be quasiperiodic with respect to the quantized Cooper-pair charge. Integrating this element into a larger circuit opens the door towards the engineering of an even broader class of systems. First, we use it to simulate a protected Dirac material defined in the transport degrees of freedom. The presence of the Dirac points leads to a suppression of the classical part of the finite-frequency noise. Second, we exploit the quasiperiodicity to implement the Aubry-André model, and thereby emulate Anderson localization in charge space. Our setup implements a truly non-interacting version of the Aubry-André model, in which the macroscopic quantum mechanics of the circuit already incorporates microscopic interaction effects. We propose that measurements of the quantum fluctuations of the charge can be used to directly probe the localization effect. |
Monday, March 6, 2023 10:12AM - 10:24AM |
A75.00010: Automated effective circuit Hamiltonian learning with autoencoders Joséphine Pazem, Mohammad H Ansari High-precision superconducting quantum processors require delicate circuit QED analysis to capture interactions originating from the low frequency domain (<10 kHz). By block-diagonalizing the circuit's Hamiltonian, effective parameters are deduced for the degrees of freedom of interest. Conventional methods, such as the Schrieffer-Wolff transformation, are limited to the perturbative regime, while alternatives, though more accurate, do not scale well beyond two qubits. With the aim to enable circuit analysis on larger systems to improve the current experiments, we propose a novel numerical approach relying on machine learning. An autoencoder network is trained to determine the effective Hamiltonian on multiple qubits in order to simulate the behavior of different gates. |
Monday, March 6, 2023 10:24AM - 10:36AM |
A75.00011: Symplectic Schrieffer-Wolff perturbation theory for superconducting circuits with nonreciprocal devices Lautaro Labarca Superconducting circuits are one of the leading platforms for realizing large-scale quantum processors. In superconducting quantum processors with a large number of qubits the characterization of effective parameters modelling the circuit is a difficult task. In this work we obtain linear effective couplings between the qubits for superconducting processors formed by low-anharmonicity qubits dispersively coupled through general linear (non)reciprocal devices by applying a full-fledged symplectic version of the Schrieffer-Wolff transformation. We show that the analytical expressions of such couplings are connected to the immittance response matrices of the system. Our work extends the quantum engineer's toolbox to characterize and design processors of superconducting circuits. |
Monday, March 6, 2023 10:36AM - 10:48AM |
A75.00012: Gyrators, quantum wormholes, and exceptional points Roman-Pascal Riwar, Ahmed Kenawy, Mohammad Atif Javed, Tobias Herrig, Christina Koliofoti, Daniel Kruti, Oleksiy Kashuba The symbiosis of ideas between the communities of high energy and condensed matter physics has a long and fruitful tradition, be it the elusive Majorana fermion, BCS theory serving as the blueprint for the Higgs mechanism, or the plethora of relativistic effects in graphene and Weyl semimetals. The condensed matter viewpoint helped in particular to elucidate some of the more obscure features of Hawking radiation, most prominently in ultra-cold atoms. However, in order to generate apparent event horizons, it seemed up until now indispensable to keep the system in a continuously driven state – rendering black holes only meaningful for open systems. We here propose for the first time a pure circuit-QED realization of a quantum wormhole, with gyrators and Josephson junctions as the main protagonists. While the emerging Hawking radiation is similar to other previously studied systems, the circuit realization adds one important new ingredient: quantum fields that are compact due to charge quantization. This allows for creating the necessary "overtilt" of the light cone by using a single quantum quench, but otherwise letting the system evolve autonomously. In addition, we are able to understand the generation of the radiation in terms of exceptional points, which here emerge somewhat unexpectedly, to describe the transient dynamics of a closed system instead of the usual open system. We thus aim to show that superconducting circuits provide a novel and highly accessible testbed for quantum gravitational effects. |
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