Dispersive gate-sensing of a quantum dot coupled to a superconducting island

ORAL

Abstract

Combining superconductivity with quantum dots in proximitized, semiconducting nanowires has led to many novel phenomena ranging from π-junctions to Cooper-pair splitters. Currently, these hybrid systems are of interest in the context of Majorana-zero modes (MZMs). In particular, it has been proposed that a topological qubit can be made by coupling a superconducting island hosting MZMs to a dot. However, to date, even trivial superconducting island-dot systems are not yet fully understood.

To increase this understanding, we experimentally study the coupling between a quantum dot and a superconducting island. Dispersive gate-sensing is used to readout because it is directly sensitive to the coupling amplitude between the two systems. We focus on two regimes characterized by their coupling to the leads. For weak, but finite, lead coupling, we identify the relevant charge-transfer processes by comparing a phenomenological model to our data. For a closed system without lead coupling, we can access quasiparticle states allowing us to extract the free energy difference of the island.

Combined, these experiments set the stage for future dot-MZMs experiments. This is necessary for distinguishing dot-trivial superconductor coupling from dot-MZM coupling.

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Presenters

  • Jasper Van Veen

    QuTech and Kavli Institute of NanoScience, Delft University of Technology, Delft University of Technology, QuTech, Delft University of Technology

Authors

  • Jasper Van Veen

    QuTech and Kavli Institute of NanoScience, Delft University of Technology, Delft University of Technology, QuTech, Delft University of Technology

  • Damaz de Jong

    QuTech and Kavli Institute of NanoScience, Delft University of Technology

  • Lin Han

    QuTech and Kavli Institute of NanoScience, Delft University of Technology

  • Christian Prosko

    QuTech and Kavli Institute of NanoScience, Delft University of Technology

  • Torsten Karzig

    Microsoft Station Q, Microsoft Quantum, Station Q, Microsoft Corp, Station Q, Microsoft, Station-Q, Microsoft Research, Microsoft Corp, Microsoft

  • Peter Krogstrup

    Niels Bohr Institute, Center for Quantum Devices and Microsoft Quantum Lab--Copenhagen, Niels Bohr Institute, University of Copenhagen, Center for Quantum Devices, Niels Bohr Institute, Center for Quantum Devices and Station-Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Station Q, Microsoft, Microsoft Corp

  • Jesper Nygård

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

  • Leo P Kouwenhoven

    Microsoft Station Q at Delft University of Technology, Microsoft Quantum Delft, Qutech, Delft University of Technology, QuTech, Delft University of Technology, Station Q Delft, Microsoft, Microsoft Station Q Delft, Microsoft Station-Q at Delft University of Technology, Microsoft Station Q Delft, Delft University of Technology

  • John Watson

    Microsoft Quantum Delft, Microsoft Station-Q at Delft University of Technology, Microsoft Station Q Delft, Delft University of Technology

  • Wolfgang Pfaff

    Microsoft Station-Q at Delft University of Technology, Microsoft Station Q Delft, Delft University of Technology, Microsoft