Suppression of charge dispersion by resonant tunneling in a single-channel transmon qubit

ORAL

Abstract

Motivated by the importance of understanding the underlying charge physics in superconducting qubits, we investigate the charge dispersion of a gate-controlled nanowire-based transmon. When approaching the pinch-off regime of the nanowire junction, we observe resonant behavior of the plasma frequency, which we attribute to the formation of a quantum dot in the junction. By measuring the charge dispersion while crossing a resonance, we observe that it is suppressed far below the range expected for a conventional transmon at comparable values of the Josephson and charging energies. The enhanced suppression can be explained and quantitatively modeled by the presence, at resonance, of a single transport channel with near-unity transmission. Our results establish an experimental validation of the theory of Coulomb oscillations in Josephson junctions in a previously unexplored regime. In addition, these results show that charge dispersion can be suppressed without the necessity of large EJ/EC ratios, potentially allowing a very large qubit anharmonicity.

*This work was supported by Microsoft and the Danish National Research Foundation.

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Presenters

  • Anders Kringhøj

    • Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
    • Univ of Copenhagen

Authors

  • Anders Kringhøj

    • Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
    • Univ of Copenhagen

  • Bernard Van Heck

    • Microsoft Quantum Lab Delft, Delft University of Technology, 2600 GA Delft, The Netherlands
    • Microsoft
    • Quantum Lab Delft, Microsoft
    • Microsoft Quantum Lab Delft

  • Thorvald Larsen

    • Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
    • Microsoft

  • Oscar Erlandsson

    • Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
    • Univ of Copenhagen

  • Deividas Sabonis

    • Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
    • Univ of Copenhagen

  • Peter Krogstrup

    • Microsoft Quantum Materials Lab and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Kanalvej 7, 2800 Kongens Lyngby, Denmark
    • Microsoft
    • Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Materials Lab Copenhagen
    • Quantum Materials Lab Copenhagen, Microsoft
    • Center for Quantum Devices and Microsoft Quantum Lab–Copenhagen
    • Center for Quantum Devices and Microsoft Quantum Lab Copenhagen, Niels Bohr Institute, University of Copenhagen
    • Microsoft Corp

  • Lucas Casparis

    • Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark

  • Karl Petersson

    • Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
    • Microsoft
    • Niels Bohr Inst
    • Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark

  • Charles Marcus

    • Center for Quantum Devices and Microsoft Quantum Lab Copenhagen, Niels Bohr Institute, University of Copenhagen
    • Microsoft Quantum Lab Copenhagen and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
    • Univ of Copenhagen
    • Center for Quantum Devices and Microsoft Quantum Lab - Copenhagen, University of Copenhagen
    • Center for Quantum Devices, Microsoft Quantum Lab – Copenhagen and Niels Bohr Institute, University of Copenhagen
    • Microsoft Corp
    • Niels Bohr Institute, University of Copenhagen