Efficient Qubit Readout Using Josephson Photomultipliers

ORAL

Abstract

A Josephson photomultplier (JPM) -- a current-biased Josephson junction operated near its critical bias -- can absorb and detect weak microwave signals with high sensitivity (PRL 107, 217401 (2011)). When strongly coupled to a high-Q transmission line ``cavity,'' the JPM can detect single microwave photons with large bandwidth and with near unit efficiency (PRB 86, 174506 (2012)). The switching of a JPM into its voltage state acts on the adjacent cavity via the backaction of photon subtraction (PRA 86, 032311 (2012)). While a destructive measurement of the microwave cavity, this switching can perform a binary non-demolition measurement of a quantum system coupled to the cavity. We present a protocol by which the presence and subsequent detection of a cavity photon by a JPM conveys information about the state of a superconducting qubit without destroying it, thus performing a quantum non-demolition measurement of the qubit's state. Multi-qubit generalizations of this protocol are discussed.

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Authors

  • E.J. Pritchett

    • Saarland University

  • L.C.G. Govia

    • Saarland University

  • Canran Xu

    • University of Wisconsin
    • University of Wisconsin-Madison
    • Univ of Wisconsin, Madison

  • Maxim Vavilov

    • University of Wisconsin
    • University of Wisconsin - Madison
    • University of Wisconsin-Madison
    • Univ of Wisconsin, Madison
    • Department of Physics, University of Wisconsin, Madison, WI

  • Britton Plourde

    • Syracuse University

  • Robert McDermott

    • University of Wisconsin, Madison
    • University of Wisconsin
    • University of Wisconsin-Madison

  • F.K. Wilhelm

    • Saarland University
    • Univ des Saarlandes
    • Universit\"at des Saarlandes