Stroboscopic detection of itinerant microwave photons

TL;DR

This paper proposes a new method for detecting single microwave photons using Josephson-photonics devices, achieving high efficiency and low dark counts through stroboscopic measurement and photon multiplication.

Contribution

It introduces a novel stroboscopic detection scheme for itinerant microwave photons with optimized measurement protocols and demonstrates near-unity efficiency with cascading devices.

Findings

Detection efficiency of 88.5% achieved

Dark count rate around 10^{-4} gamma_a

Potential for near-unity efficiency with higher multiplication factors

Abstract

We present a novel scheme to detect itinerant microwave radiation at the single photon level. Using existing Josephson-photonics devices, where two microwave cavities are coupled by a dc-voltage biased superconducting junction, we theoretically show how to implement a stroboscopically repeated, near-projective measurement of a photon impinging on one of the cavities. Optimizing rate, duration, and strength of the measurement by flux control of the junction and developing a threshold protocol to detect the photon from a homodyne measurement of the radiation output of the other cavity, we achieve highly efficient detection with low dark counts. By cascading the detector with a preamplifier, where a similar two-cavity Josephson-photonics device acts as a photon multiplier, we can further improve the device to reach a detection efficiency of $88.5 \%$ with a dark count rate of $\sim10^{-4} \gamma_a$, set by the resonance width $\gamma_a$ of the absorbing cavity. These results for a multiplication factor of two suggest that near-unity efficiencies may be reached for higher multiplication factors.