Nonreciprocity detector arrays for high-efficiency detection of itinerant microwave photons

Microwave single-photon detection is one of the critical tasks for the implementation of the desired microwave quantum information processing. Given the detection efficiency of the demonstrated microwave single-photon detector is still very limited, here, we propose a nonreciprocity detector array to implement high-efficiency detection of a single itinerant microwave photon, transported along a one-dimensional waveguide. We show that different from the reciprocity array with more than 20 atomic detectors [Romero et al., Phys. Rev. Lett. 102, 173602 (2009)] for ideal detection, the nonreciprocity array with just three atomic detectors is sufficient to achieve deterministic detection (i.e., the achievable probability approaches $100%$) of a single itinerant microwave photon. Specifically, we design an array with a few current-biased Josephson junctions individually coupled to a common microwave transmission line and then discuss its feasibility.