Measuring Quasi-particle Tunneling Rates in Transmon Qubits

ORAL

Abstract

The tunneling of non-equilibrium quasiparticles (QPs) across the Josephson junction of superconducting qubits is a source of energy loss and dephasing, resulting in a reduced coherence time. To measure changes in the charge parity rate between the two pads of a transmon qubit, we have designed transmons with a charge dispersion approximately 6 MHz between the first excited |e> and the second excited states |f>. The designed transmons allow fast mapping of the charge parity rate while maintaining a good charge-noise protection between the |g> and |e> states. Using a modified Ramsey pulse sequence on the |e> to |f> states, we monitor temporally the effective charge parity of the qubits. For some Al qubits, we compare the measured charge parity rates to T1 with and without a direct galvanic connection to the ground plane.

*We acknowledge MIT Lincoln Laboratory for fabrication of the transmon device.

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Presenters

  • Yi-Hsiang Huang

    • University of Maryland, College Park

Authors

  • Yi-Hsiang Huang

    • University of Maryland, College Park

  • Yizhou Huang

    • University of Maryland, College Park; Quantum Materials Center, University of Maryland, College Park
    • University of Maryland, College Park

  • Zachary Steffen

    • University of Maryland, College Park; Quantum Materials Center, University of Maryland, College Park
    • University of Maryland, College Park

  • Haozhi Wang

    • University of Maryland, College Park; Quantum Materials Center, University of Maryland, College Park
    • University of Maryland, College Park

  • Kungang Li

    • University of Maryland, College Park; Quantum Materials Center, University of Maryland, College Park
    • University of Maryland, College Park

  • Sudeep K Dutta

    • University of Maryland, College Park; Quantum Materials Center, University of Maryland, College Park
    • University of Maryland, College Park

  • Frederick C Wellstood

    • University of Maryland, College Park; Quantum Materials Center, University of Maryland, College Park
    • University of Maryland, College Park

  • Benjamin S Palmer

    • Laboratory for Physical Sciences; Quantum Materials Center, University of Maryland, College Park
    • Laboratory for Physical Sciences, Quantum Materials Center, University of Maryland
    • Laboratory for Physical Sciences