Switching Times of Josephson Junctions for Single Photons Detection

In the past two decades, the development of nanotechnologies and superconducting materials has led to the possibility to design ultrasensitive sensors for very weak signals, even close to the quantum limit. Among the superconducting elements, Josephson junctions (JJs) stand as a promising candidate to detect weak microwave signals, or even single microwave photons. The detection in this range of frequencies, that is below the terahertz band, is challenging, for the energy of a photon is comparable to thermal energy. JJs are promising for they operate in the range of microwave region and being superconducting elements can be cooled as much as cryogenics allow[1, 2]. In a suitable configuration for photon detection, a JJ is exposed to a microwave field that induces the appearance of a voltage, as the perturbation induces a switch from the superconducting to the resistive state. In this set-up, the confounding thermal-induced transitions are to be kept at bay lowering the operating temperature, for they produce spurious events that corrupt the detection process. In this talk we show how to carefully plan Josephson-based experiments devised to decide about the existence of a weak electromagnetic signal in a thermal noise background, and to achieve the best conditions to reveal the photon field in the frame of signal detection [3, 4]. The analysis considers a JJ prepared in the superconducting state, and proposes to collect the waiting times of the device prior to a switch towards the finite voltage state [5, 6]. The employed methodology consists in comparing the switching probabilities of a junction exposed to a train of current pulses, which mimics a weak photon field, with that of the same device in absence of pulses. The investigation of the unbalance in the number of switching events in the two cases, gives an estimate of the efficiency of the detection. The optimization of the detection probability will give a guide to select the JJ parameters that best suit to reveal weak microwave signals. 1. Alesini, D., et al., “Status of the simp project: Toward the single microwave photon detection”, Journal of Low Temperature Physics 199, 348 (2020). 2. Alesini, D., et al., “Development of a Josephson junction based single photon microwave detector for axion detection experiments”, Journal of Physics: Conference Series 1559, 012020 (2020). 3. Filatrella, G. and Pierro, V. “Detection of noise-corrupted sinusoidal signals with Josephson junctions”, Phys. Rev. E, 82, 0467121-9 (2010) 4. Addesso, P., et al. “Characterization of escape times of Josephson junctions for signal detection”, Phys. Rev. E, 85, 016708 (2012) 5. Piedjou Komnang, A., et al. “Analysis of Josephson junctions switching time distributions for the detection of single microwave photons”, Chaos Solitons Fract 142, 110496 (2021) 6. Filatrella, G., et al. “Analysis of thermal and quantum escape times of Josephson junctions for signal detection” in publications in 13th Chaotic Modeling and Simulation International Conference (2021)