Advances in Single Microwave Photon Detection*

Circuit Quantum Electrodynamics (CQED) has not only been at the forefront of quantum computing but also shows promise for quantum sensing applications. Specifically, the Single Microwave Photon Detector (SMPD) leverages the transformation of a traveling photon state into a qubit excitation via a 4-wave mixing parametric process. This technique marked a milestone by enabling the detection of individual electron spins and achieved a sensitivity as high as 10^-22 W/√Hz [1].

In this presentation, we introduce an enhanced SMPD architecture that promises a significant reduction in the detector's dark count rate. Our research further lays the groundwork for diverse applications in single microwave photon sensing, including the detection of crystal impurities, characterization of individual molecules, and the pursuit of dark matter.

[1] L. Balembois, et al. Practical Single Microwave Photon Counter with 10^-22 W/√Hz sensitivity. arXiv:2307.03614.