High-fidelity qubit measurement with a microwave-photon counter

Luke C.G. Govia, Emily J. Pritchett, Canran Xu, B. L.T. Plourde, Maxim G. Vavilov, Frank K. Wilhelm, R. McDermott

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


High-fidelity, efficient quantum nondemolition readout of quantum bits is integral to the goal of quantum computation. As superconducting circuits approach the requirements of scalable, universal fault tolerance, qubit readout must also meet the demand of simplicity to scale with growing system size. Here we propose a fast, high-fidelity, scalable measurement scheme based on the state-selective ring-up of a cavity followed by photodetection with the recently introduced Josephson photomultiplier (JPM), a current-biased Josephson junction. This scheme maps qubit state information to the binary digital output of the JPM, circumventing the need for room-temperature heterodyne detection and offering the possibility of a cryogenic interface to superconducting digital control circuitry. Numerics show that measurement contrast in excess of 95% is achievable in a measurement time of 140 ns. We discuss perspectives to scale this scheme to enable readout of multiple qubit channels with a single JPM.

Original languageEnglish (US)
Article number062307
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Issue number6
StatePublished - Dec 2 2014

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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