Microwave Photon Counter Based on Josephson Junctions

TL;DR

This paper presents a microwave photon counter using Josephson junctions that can detect single photons and perform quantum optics experiments, with potential for scalable photon number resolution.

Contribution

The work introduces a Josephson junction-based microwave photon counter capable of single-photon detection and demonstrates its application in measuring photon bunching.

Findings

Successful detection of single microwave photons.

Observation of photon bunching in a thermal source.

Scalability potential for photon number-resolved counting.

Abstract

We describe a microwave photon counter based on the current-biased Josephson junction. The junction is tuned to absorb single microwave photons from the incident field, after which it tunnels into a classically observable voltage state. Using two such detectors, we have performed a microwave version of the Hanbury Brown and Twiss experiment at 4 GHz and demonstrated a clear signature of photon bunching for a thermal source. The design is readily scalable to tens of parallelized junctions, a configuration that would allow number-resolved counting of microwave photons.