Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session W41: Engineered Superconducting Qubit InteractionsFocus Recordings Available
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Sponsoring Units: DQI Chair: Mollie Schwartz, MIT Lincoln Laboratory Room: McCormick Place W-196C |
Thursday, March 17, 2022 3:00PM - 3:12PM |
W41.00001: Dynamics of coupled superconducting oscillators at high drive power: a time-coarse graining approach Wentao Fan, Hakan E Tureci, Kanupriya Sinha We present a computationally efficient theoretical approach to accurately capture the dynamics of coupled quantum non-linear oscillators at high drive power embedded in an environment with a given spectral function. We take the point of view that the most resource-efficient approach should both require and provide no more and no less information than what can be measured in a particular experiment. We posit that one possible approach to do that is through time-coarse graining starting with the full Hamiltonian of the system and the environment with a well-characterized spectral function. A systematic derivation of effective (low frequency) quantum models is presented for basic models of interest in superconducting quantum systems. Specifically, we present the drive-dependent renormalized Hamiltonian and dissipative super operators of a driven Josephson non-linear oscillator coupled to a 50-ohm transmission line through a linear resonator. |
Thursday, March 17, 2022 3:12PM - 3:24PM |
W41.00002: Optimization of two-qubit gate rates and crosstalk in a tunable coupling superconducting device Camille Le Calonnec, Alexandru Petrescu, Catherine Leroux, Agustin Di Paolo, Sara F Sussman, Charles Guinn, Pranav S Mundada, Andrei Vrajitoarea, Alexander P Place, Andrew A Houck, Alexandre Blais The implementation of fast and high-fidelity quantum gates involves a multitude of parameters governing important properties of the system, such as the gate rate, leakage and the extent of spurious interactions. One therefore needs to carefully choose these parameters to optimize the gate fidelity and speed. We study the case of two far detuned fixed frequency transmons coupled through a flux-tunable coupler. Here, we present the results of a parameter search run to maximize gate rates while minimizing unwanted cross-Kerr interaction using a method based on Floquet theory. We also estimate variations on the quantities of interest due to imprecision in device fabrication. Finally, we study spectator effects in a multi-qubit chip. |
Thursday, March 17, 2022 3:24PM - 3:36PM |
W41.00003: Fast parametrically driven entangling gates in superconducting circuits using a tunable coupler Charles Guinn, Sara F Sussman, Pranav S Mundada, Andrei Vrajitoarea, Catherine Leroux, Alexander P Place, Camille Le Calonnec, Agustin Di Paolo, Alexandru Petrescu, Alexandre Blais, Andrew A Houck A major challenge in realizing scalable quantum computers is the optimization of two-qubit entangling gates. In current superconducting architectures, ZZ crosstalk introduces unwanted entanglement while slow gates push fidelities down due to decoherence. It is thus desirable to make entangling gates as fast as possible while maintaining control over multi-qubit interactions. In this work we demonstrate a tunable coupler that can be flux biased to mitigate ZZ crosstalk while allowing fast parametrically driven two-qubit entangling gates between far-detuned fixed-frequency transmons. |
Thursday, March 17, 2022 3:36PM - 4:12PM |
W41.00004: PIQUE: a new framework for quantum systems engineering Invited Speaker: Archana Kamal High-fidelity quantum state preparation, manipulation, and measurement are the three cornerstones of any quantum information processing platform. In this talk I will describe a new paradigm called PIQUE (for Parametrically-Induced QUantum Engineering), which tackles all three challenges in a unified framework employing Josephson junction-based parametric circuits. I will first discuss some novel functionalities for quantum state stabilization and readout afforded by strong parametric interactions, which build upon and advance state-of-the-art capabilities of circuit-QED architectures. Next, I will discuss some new opportunities enabled by parametric systems for the exploration of fundamental open quantum system physics. |
Thursday, March 17, 2022 4:12PM - 4:24PM |
W41.00005: "Minimal" topological quantum circuit Tobias Herrig, Roman-Pascal Riwar The outlook of protected quantum computing spurred enormous progress in the search for topological materials, sustaining a continued race to find the most experimentally feasible platform. Here, we show that one of the simplest quantum circuits, the Cooper-pair transistor, exhibits a nontrivial Chern number which has not yet been discussed, in spite of the exhaustive existing literature. Surprisingly, the resulting quantized current response is robust with respect to a large number of external perturbations, most notably low-frequency charge noise and quasiparticle poisoning. Moreover, the fact that the higher bands experience crossings with higher topological charges leads to all the bands having the same Chern number, such that there is no restriction to stay close to the ground state. Remaining small perturbations are investigated based on a generic Master equation approach. Finally, we discuss a feasible protocol to measure the quantized current. |
Thursday, March 17, 2022 4:24PM - 4:36PM |
W41.00006: Single Shot i-Toffoli Gate in Dispersively Coupled Superconducting Qubits Aneirin J Baker, Michael J Hartman, Ivan Tsitsilin, Federico Roy, Gehard Huber, Niklas Glaser, Stefan Filipp Quantum algorithms often benefit from the ability to execute multi-qubit (>2) gates. To date such multi-qubit gates are typically decomposed into single- and two-qubit gates, particularly in superconducting qubit architectures. The ability to perform multi-qubit operations in a single step could vastly improve the fidelity and execution time of many algorithms. |
Thursday, March 17, 2022 4:36PM - 4:48PM |
W41.00007: Automating Quantization and Diagonalization of Superconducting Circuits Sai Pavan Chitta, Jens Koch The analysis of superconducting circuits currently consists of a multi-step process combining analytical and numerical elements that together enable the transition from a lumped-element circuit diagram to a quantum Hamiltonian ready to be diagonalized. Important aspects include the choice of appropriate circuit variables, incorporation of constraints imposed by Kirchhoff's laws, the elimination of cyclic variables, and the distinction of degrees of freedom subject to periodic versus confining boundary conditions upon quantization. We present work that systematizes these steps in a manner amenable to algorithmic implementation, thus opening the pathway for streamlined and efficient analysis of unexplored superconducting circuits to serve as qubits, tunable couplers, and similar parts of quantum processors. A concrete implementation of this circuit quantization tool is made available as an extension to the open-source scqubits package. |
Thursday, March 17, 2022 4:48PM - 5:00PM |
W41.00008: Liberating Quantum Processors from Parasitic Interactions Mohammad H Ansari I explain two methods for zeroing parasitic interaction between a pair of qubits. A year ago, for the first time we showed that magnetic modulation helps to set the interaction to zero in a hybrid circuit containing a transmon coupled to a flux qubits. Most recently we developed the theory and showed the possibility of zeroing parasitic interaction in non-modulable fixed parameter qubits. For this we need to use microwave driving, and we named this technique "dynamic cancellation." This owes to a fundamental symmetry in the Hamiltonian of superconducting processors. Using our understanding of parasitic interactions and how to eliminate them, one can aim for perfect two qubit gate. One example I show is PF gate. |
Thursday, March 17, 2022 5:00PM - 5:12PM |
W41.00009: Three-Qubit Parasitic Interactions in Superconducting Circuits Xuexin Xu, Mohammad H Ansari Superconducting qubits have proven to be an excellent candidate for quantum computing. But because of the imperfections in the gate fidelity of these qubits, making a giant network with many coupled qubits is still a far fetched dream. A much needed in-depth study is required to understand the nature of qubit-qubit couplings, especially the so-called parasitic interactions in order to minimize the leakage and have a much-improved gate fidelity. We study the Hamiltonian of a circuit containing multiple superconducting qubits coupled via shared resonators. We derive, both analytically and numerically, the parasitic multi-Z interactions for such a system. We also provide possible parameter regimes to minimize the parasitic interactions in order to achieve higher fidelity gate implementations for larger circuits. |
Thursday, March 17, 2022 5:12PM - 5:24PM |
W41.00010: Ultrastrong capacitive and inductive couplings of flux qubits María Hita-Pérez, Gabriel Jaumà, Manuel Pino Garcia, Juan Jose Garcia-Ripoll
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Thursday, March 17, 2022 5:24PM - 5:36PM |
W41.00011: Generating families of three-qubit gates from simultaneous two-qubit gates, part 1: theory Anton Frisk Kockum, Xiu Gu, Jorge Fernández-Pendás, Pontus Vikstål, Tahereh Abad, Christopher W Warren, Andreas Bengtsson, Giovanna Tancredi, Vitaly Shumeiko, Jonas Bylander, Göran Johansson Decoherence of qubits limits near-term quantum computers to only run low-depth quantum circuits with acceptable fidelity. This severely restricts what quantum algorithms can be compiled and implemented on such devices. One way to overcome these limitations is to expand the available gate set from single- and two-qubit gates to multi-qubit gates, which entangle three or more qubits in a single step. Here, we show that such multi-qubit gates can be realized by the simultaneous application of multiple two-qubit gates to a group of qubits where at least one qubit is involved in two or more of the two-qubit gates. Multi-qubit gates implemented in this way are as fast as, and often even faster than, the constituent two-qubit gate operations. Importantly, these multi-qubit gates are ready to be used in current quantum-computing platforms without any modification of the quantum processor. We demonstrate this idea for two specific cases: simultaneous controlled-Z gates and simultaneous iSWAP gates. We show how the resulting multi-qubit gates relate to other well-known multi-qubit gates and simulate gate fidelities well above 99%. |
Thursday, March 17, 2022 5:36PM - 5:48PM |
W41.00012: Generating families of three-qubit gates from simultaneous two-qubit gates, part 2: experiment Christopher W Warren, Anton Frisk Kockum, Jorge Fernández Pendás, Shahnawaz Ahmed, Giovanna Tancredi, Amr Osman, Janka Biznárová, Xiu Gu, Göran Johansson, Jonas Bylander Whether one is working on noisy intermediate-scale quantum (NISQ) algorithms or towards error correction, the coherence of a quantum processor sets bounds on the depth which can be achieved for any sequence of operations. Each of these cases requires the generation of large, entangled states. This is typically achieved by implementing a universal gate set formed of single- and two-qubit operations. While generating these states is achievable, as devices grow larger in terms of the number of qubits, the depth needed to entangle all qubits increases. |
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