The detection of microwave fields at single-photon power levels is a much sought-after technology, with practical applications in nanoelectronics and quantum information science. Here we demonstrate a simple yet powerful criticality-enhanced method of microwave photon detection by operating a magnetic-field tunable Kerr Josephson parametric amplifier at the border of a first-order phase transition and close to the critical point. We obtain a 73\% efficiency and a dark-count rate of 167 kHz, corresponding to a responsivity of 1.3×1017W−1 and noise-equivalent power of 3.28 zW/Hz. We verify the single-photon operation by extracting the Poissonian statistics of a coherent probe signal.
@article{arxiv.2308.07084,
title = {Microwave photon detection at parametric criticality},
author = {Kirill Petrovnin and Jiaming Wang and Michael Perelshtein and Pertti Hakonen and Gheorghe Sorin Paraoanu},
journal= {arXiv preprint arXiv:2308.07084},
year = {2025}
}