Photon response induced by single quantum phase slip of superconducting nanowire single photon detector

The superconducting nanowire single photon detector (SNSPD) is currently one of the best detectors with comprehensive performance in the mid-infrared wavelength, which has been widely used in quantum optics, LiDAR, and biological fluorescence detection. To develop new devices with excellent performance, the photon detection mechanism of SNSPD still needs further research. Here we find that the single quantum phase slip is the dominating mechanism leading to dark-count and photon-response events in SNSPD below the quantum temperature. We fabricate the nanowire with a length of 7.5 μm and a width of 25 nm using niobium nitride film with a thickness of 5 nm. The distribution of the superconducting switching current is measured as a function of temperature at temperatures ranging from 0.3 to 7 K. We observe single quantum phase slips in the nanowire at the temperature below 1.2 K, and we further investigate the quantitative relationship between the single quantum phase slip rate and the superconducting switching rate of the nanowire under the laser illumination. Experimental results show that the single quantum phase slip is a significant factor leading to photon response and dark counts in the nanowire below the quantum temperature. Our research helps to further reveal the photon detection mechanism of the SNSPD, laying a theoretical foundation for the development of high-performance SNSPD.