Temperature Dependence of Kinetic Inductance in a WSi Superconducting Nanowire Single-Photon Detector*

There is currently great interest in developing detectors for efficiently measuring single photons for applications in quantum information science. One appealing platform is the superconducting nanowire single-photon detector (SNSPD). Here, a single photon absorbed by a nanowire of superconductor causes a region of the wire to transition to the normal (nonsuperconducting) state, which can be sensed by passing a small current through the device. The timing jitter and reset time of the detector is related to the kinetic inductance ($L_k$) of the nanowire that arises from the ballistic motion of Cooper pairs through the device. Thus, it is important to understand how this inductance depends on device parameters, such as the current passing through the device as well as the temperature. Recent work has shown that $L_k$ diverges when the nanowire is heated to $T_c$, which has implications in the development of novel superconducting devices. Here, we measure $L_k$ for various temperatures in a WSi SNSPD by fitting the falling edge of measured single-photon pulses.