Dephasing in fluxonium qubits from coherent quantum phase slips

ORAL

Abstract

Phase slips occur at all Josephson junctions (JJs) at a rate dependent on the junction impedance. In superconducting qubits comprised of JJ array superinductors, such as fluxonium, phase slips in the array can lead to decoherence. In particular, phase slip processes at the individual array junctions can coherently interfere, each with an Aharonov-Casher phase dependent on the offset charges of the array islands. These coherent quantum phase slips (CQPS) perturbatively modify the qubit frequency, therefore charge noise on the array islands will lead to dephasing. By varying the impedance of the array junctions, we specifically engineer a set of fluxonium qubits to be sensitive to CQPS-induced dephasing over three orders of magnitude. We characterize the coherence times of these qubits in regimes dominated by CQPS or flux noise and show agreement with theoretical models. A detailed understanding of this dephasing mechanism has implications for improvements to coherence in fluxonium and is relevant for the many novel qubit designs involving JJ arrays.

This material is based upon work supported under Air Force Contract No. FA8702-15-D-0001. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. government or the U.S. Air Force.

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Presenters

  • Mallika T Randeria

    MIT Lincoln Laboratory

Authors

  • Mallika T Randeria

    MIT Lincoln Laboratory

  • Thomas M Hazard

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

  • Agustin Di Paolo

    Massachusetts Institute of Technology, Google Quantum AI

  • Kate Azar

    MIT Lincoln Laboratory, Wellesley Coll

  • Max Hays

    MIT, Massachusetts Institute of Technology (MIT), Massachusetts Institute of Technology MI, Massachusetts Institute of Technology, Massachussets Institute of Technology, Massachusetts Institute of Technology MIT

  • Leon Ding

    Massachusetts Institute of Technology MI, Massachusetts Institute of Technology

  • Junyoung An

    Massachusetts Institute of Technology MI, Massachusetts Institute of Technology

  • Hannah M Stickler

    MIT Lincoln Laboratory

  • Michael A Gingras

    MIT Lincoln Laboratory

  • Bethany M Niedzielski

    MIT Lincoln Lab, MIT Lincoln Laboratory

  • Jeffrey A Grover

    Massachusetts Institute of Technology, Massachusetts Institute of Technology (MIT), Massachusetts Institute of Technology MIT

  • Jonilyn L Yoder

    MIT Lincoln Lab, MIT Lincoln Laboratory

  • Mollie E Schwartz

    MIT Lincoln Laboratory

  • William D Oliver

    Massachusetts Institute of Technology MI, Massachusetts Institute of Technology, Massachusetts Institute of Technology (MIT), Massachusetts Institute of Technology MIT

  • Kyle Serniak

    MIT Lincoln Laboratory & MIT RLE, MIT Lincoln Laboratory, MIT Lincoln Laboratory, MIT RLE