Evolution of Nanowire Transmons and Their Quantum Coherence in Magnetic Field

 · Invited

Abstract

Extending the range of application of circuit QED to magnetic fields of order 0.5 T promises interesting applications, including the control and readout of Majorana systems and the coupling to electron-spin systems. In this talk, we present an experimental study of nanowire transmon qubits with state-of-the-art relaxation and dephasing times exceeding 10 μs at zero magnetic field. We investigate the evolution of transmon transition frequencies, anharmonicity, and coherence up 70 mT, limited by the closing of the superconducting gap induced in the InAs nanowire by the thick, epitaxially contacting Al shell. We investigate various sources contributing to the decoherence. In particular, we find that, unlike in conventional transmons, on-chip charge noise coupling to the Josephson energy plays a dominant role in qubit dephasing. This noise takes the form of strongly-coupled two-level systems switching on 100 ms timescale and a more weakly coupled background producing 1/f noise. We conclude with an update on ongoing efforts to extend operation to 0.5 T using nanowires contacted with thinner, partially covering Al shells.

*We acknowledge funding by Microsoft Corporation Station Q, the Dutch organization for Fundamental Research on Matter (FOM), the Netherlands Organization for Scientific Research (NWO), an ERC Synergy grant, and the Danish National Research Foundation.

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Presenters

  • Florian Luthi

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

Authors

  • Florian Luthi

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Thijs Stavenga

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Oscar Enzing

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Alessandro Bruno

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology
    • Kavli Institute of Nanoscience Delft, Delft University of Technology
    • QuTech, Delft Univ. of Technology

  • Christian Dickel

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Nathan Langford

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Michiel Adriaan Rol

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • David Thoen

    • Kavli Institute of Nanoscience and Department of Microelectronics, Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology

  • Akira Endo

    • Kavli Institute of Nanoscience and Department of Microelectronics, Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology

  • Thomas Jespersen

    • Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen

  • Jesper Nygard

    • Center for quantum devices, Niels Bohr Institute
    • Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute
    • Center for Quantum Devices and Station-Q Copenhagen, Niels Bohr Institute, University of Copenhagen
    • Center for Quantum Devices, Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen
    • Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen
    • Center of Quantum Devices and Nano-Science Center, Niels Bohr Institute, University of Copenhagen

  • Peter Krogstrup

    • Niels Bohr Inst and Microsoft Station Q
    • Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen
    • Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen

  • Leonardo DiCarlo

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology
    • TUD Faculty of Sciences, QuTech
    • Kavli Institute of Nanoscience Delft, Delft University of Technology