Superconductor-superconductor bilayers for enhancing single-photon detection.

Here, we optimized ultrathin films of granular NbN on SiO2 and of amorphous alpha W5Si3. We showed that hybrid superconducting nanowire single-photon detectors (SNSPDs) made of 2 nm thick alpha W5Si3 films over 2 nm thick NbN films exhibit advantageous coexistence of timing (< 5 ns reset time and 52 ps timing jitter) and efficiency (> 96% quantum efficiency) performance. We discuss the governing mechanism of this hybridization via the proximity effect. Our results demonstrate saturated SNSPDs performance at 1550 nm optical wavelength and suggest that such hybridization can significantly expand the range of available superconducting properties, impacting other nano-superconducting technologies. Lastly, this hybridization may be used to tune properties, such as the amorphous character of superconducting films.