Universal gates for protected superconducting qubits using optimal control

ORAL

Abstract

In this talk I will discuss the use of quantum optimal control theory to realize quantum gates for two protected superconducting circuits: the heavy-fluxonium qubit and the 0-π qubit. Utilizing automatic differentiation facilitates the simultaneous inclusion of multiple optimization targets, allowing one to obtain high-fidelity gates with realistic pulse shapes. For both qubits, disjoint support of low-lying wave functions prevents direct population transfer between the computational-basis states. Instead, optimal control favors dynamics involving higher-lying levels, effectively lifting the protection for a fraction of the gate duration. For the 0-π qubit, offset-charge dependence of matrix elements among higher levels poses an additional challenge for gate protocols. To mitigate this issue, we randomize the offset charge during the optimization process, steering the system towards pulse shapes insensitive to charge variations. Closed-system fidelities obtained are 99% or higher, and show slight reductions in open-system simulations.

*We gratefully acknowledge support from the Army Research Office through Grant Nos. W911NF-15-1-0421 and W911NF-19-1-0016.

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Presenters

  • Brian Baker

    • Northwestern University
    • Physics and Astronomy, Northwestern University
    • Department of Physics and Astronomy, Northwestern University

Authors

  • Brian Baker

    • Northwestern University
    • Physics and Astronomy, Northwestern University
    • Department of Physics and Astronomy, Northwestern University

  • Mohamed Abdelhafez

    • University of Chicago

  • Andras Gyenis

    • Princeton University
    • Department of Electrical Engineering, Princeton University

  • Pranav Mundada

    • Princeton University
    • Department of Electrical Engineering, Princeton University
    • Electrical Engineering, Princeton University

  • Andrew Houck

    • Princeton University
    • Electrical Engineering, Princeton University
    • Department of Electrical Engineering, Princeton University

  • David I Schuster

    • University of Chicago
    • Physics, University of Chicago
    • Department of Physics and the James Franck Institute, University of Chicago
    • The James Franck Institute and Department of Physics, University of Chicago
    • The James Franck Institute and Department of Physics, The University of Chicago

  • Jens Koch

    • Northwestern University
    • Physics and Astronomy, Northwestern University
    • Department of Physics and Astronomy, Northwestern University
    • Physics, Northwestern University