Non-absorbing high-efficiency counter for itinerant microwave photons

  1. Bixuan Fan,
  2. Göran Johansson,
  3. Joshua Combes,
  4. G. J. Milburn,
  5. and Thomas M. Stace
Detecting an itinerant microwave photon with high efficiency is an outstanding problem in microwave photonics and its applications. We present a scheme to detect an itinerant microwave photon in a transmission line via the nonlinearity provided by a transmon in a driven microwave resonator. By performing continuous measurements on the output field of the resonator we theoretically achieve an over-unity signal-to-noise (SNR) for a single shot measurement and 84% distinguishability between zero and one microwave photon with a single transmon and 90% distinguishability with two cascaded transmons. We also show how the measurement diminishes coherence in the photon number basis thereby illustrating a fundamental principle of quantum measurement: the higher the measurement efficiency, the greater is the decoherence.
arxiv pdf

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