Josephson harmonics-like features in tunnel-junction SQUIDs

ORAL

Abstract

Josephson tunnel junctions are an essential element for superconducting quantum computing. However, higher Josephson harmonics of a tunnel junction, one of its fundamental physical properties, have traditionally been neglected. Recently, signatures of higher harmonics in tunnel junctions were observed in the spectra of single-junction transmons [1]. Here, we introduce a direct method to probe higher harmonics in tunnel junctions using symmetric SQUIDs. Across multiple devices with different circuit parameters, we observe a significant change in the qubit transition spectrum near half-flux that cannot be explained by the standard cosine potential. We discuss two possible models that agree with these experimental results: a Josephson harmonics model and a parasitic inductance model.

[1] D. Willsch et al., Nat. Phys. 20, 815-821 (2024)

*This research is sponsored in part by the U.S. Army Research Office under Award No.W911NFF-23-1-0045; in part by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Co-design Center for Quantum Advantage(C2QA) under contract number DE-SC0012704; and in part under Air Force Contract No.FA8702-15-D-0001. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements,either expressed or implied, of the U.S. Government.

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Presenters

  • Junghyun Kim

    • Massachusetts Institute of Technology

Authors

  • Junghyun Kim

    • Massachusetts Institute of Technology

  • Max Hays

    • MIT
    • Massachusetts Institute of Technology (MIT)
    • Massachusetts Institute of Technology

  • Junyoung An

    • Massachusetts Institute of Technology

  • Ilan T Rosen

    • Massachusetts Institute of Technology

  • Helin Zhang

    • Massachusetts Institute of Technology

  • Kate Azar

    • MIT Lincoln Laboratory

  • Jeffrey M Gertler

    • MIT Lincoln Laboratory

  • Aranya Goswami

    • Massachusetts Institute of Technology

  • Bethany M Niedzielski

    • MIT Lincoln Laboratory

  • Mollie E Schwartz

    • MIT Lincoln Laboratory
    • Lincoln Laboratory, Massachusetts Institute of Technology

  • Terry P Orlando

    • Massachusetts Institute of Technology

  • Jeffrey A Grover

    • Massachusetts Institute of Technology

  • Kyle Serniak

    • MIT Lincoln Laboratory
    • Lincoln Laboratory, Massachusetts Institute of Technology

  • William D Oliver

    • Massachusetts Institute of Technology
    • Massachusetts Institute of Technology (MIT)