Quasiparticle spectroscopy, transport, and magnetic properties of Nb films used in superconducting transmon qubits

ORAL

Abstract

Niobium films, 160 nm thick, used as leads to aluminum Josephson junctions in superconducting qubits (transmons) have been characterized using scanning and transmission electron microscopy, electrical transport, magnetization, quasiparticle spectroscopy, and magneto-optical imaging. In the Meissner state, the films show a very sharp superconducting transition at Tc = 9.35 K, a fairly clean superconducting gap, and signs of stronger coupling consistent with the recent theory of anisotropic strong-coupling superconductivity in Nb. The behavior in the applied magnetic field is complicated, exhibiting significantly irreversible behavior and insufficient heat channeling to a silicone substrate leading to thermo-magnetic dendritic avalanches. The latter may signify an issue for transmons driven at several GHz. Possible mitigation strategies are discussed.

*Supported by the DOE Office of Science, BES, MSE Division, through Ames National Laboratory under Contract No. DE-AC02-07CH11358. RP acknowledges support from the DOE NQISRC, Superconducting Quantum Materials, and Systems Center under Contract No. DE-AC02-07CH11359.

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Publication: K. R. Joshi, S. Ghimire, M. A. Tanatar, A. Datta, J.-S. Oh, L. Zhou, C. J. Kopas, J. Marshall, J. Y. Mutus, J. Slaughter, M. J. Kramer, J. A. Sauls, and R. Prozorov, Quasiparticle Spectroscopy, Transport, and Magnetic Properties of Nb Films Used in Superconducting Transmon Qubits, arXiv: 2207.11616 (2022)

Presenters

  • Kamal R Joshi

    • Ames National Laboratory
    • Iowa State University

Authors

  • Kamal R Joshi

    • Ames National Laboratory
    • Iowa State University

  • Sunil Ghimire

    • Iowa State University and Ames Laboratory
    • Ames National Laboratory
    • Iowa State University

  • Makariy A Tanatar

    • Iowa State University and Ames Laboratory
    • Ames Laboratory/Iowa State University
    • Ames National Laboratory

  • Amlan Datta

    • Ames National Laboratory

  • Jin-Su Oh

    • Ames National Laboratory

  • Lin Zhou

    • Ames Laboratory
    • Ames Lab
    • Ames National Laboratory
    • Ames Laboratory, Ames IA, USA

  • Cameron J Kopas

    • Rigetti Computing Inc
    • Rigetti Computing
    • Rigetti Quantum Computing

  • Jayss Marshall

    • Rigetti Quantum Computing

  • Josh Y Mutus

    • Rigetti Computing Inc

  • Julie Slaughter

    • Ames National Laboratory

  • Matthew J Kramer

    • Ames Laboratory
    • Ames Laboraotry
    • Ames National Laboratory

  • James A Sauls

    • Louisiana State University
    • Northwestern University

  • Ruslan Prozorov

    • Iowa State University and Ames Laboratory
    • Ames National Laboratory