Magnetic field induced 4$\pi$ periodic Josephson effect in InAs nanowires

ORAL  · Invited

Abstract

Majorana zero modes (MZM) are leading candidates to implement \emph{topological} quantum computing, owing to their predicted non-Abelian properties and their non-local protection against decoherence. While the observation of a zero-bias conductance peak in tunneling spectroscopy of nanowires strongly suggests the onset of these zero-energy states, additional proof of their existence has remained elusive. Here, we report measurements of Josephson radiation in Josephson junctions formed in a proximity-induced superconducting InAs nanowire with an epitaxially-grown Al shell. The emitted radiation is directly measured \emph{on-chip}, using photon-assisted tunneling across nearby capacitively-coupled superconducting tunnel junctions. The frequency of the detected signal evolves from a 2$\pi$ to a 4$\pi$ periodicity as the magnetic field is increased. The evolution of this transition is studied as a function of chemical potential and of transmission across the nanowire junctions. These results are interpreted using both topological and non-topological models.

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Authors

  • Dominique Laroche

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

  • Dani\"{e}l Bouman

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

  • David van Woerkom

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

  • Alex Proutski

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

  • Ruben van Gulik

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

  • Micha\l{} Nowak

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

  • Dmitry Pikulin

    • Kavli Institute for Theoretical Physics, University of California Santa Barbara

  • Jesper Nyg\r{a}rd

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

  • Peter Krogstrup

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

  • Charles Marcus

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

  • Leo Kouwenhoven

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

  • Attila Geresdi

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