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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.

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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