IR- and visible- light single photon detection in superconducting $Mg{B}_2$ nanowires

Abstract

State-of-the-art Superconducting Nanowire Single Photon Detectors based on low-Tc materials reach 100% quantum efficiency. However, the response time is limited to >1-10 ns. Recently, it has been shown that due to a much lower kinetic inductance, a 100 ps response rate can be achieved in 120 $\mu$m-long $Mg{B}_2$ nanowires. In this work, we demonstrate experimentally that such $Mg{B}_2$ nanowires function as single-photon detectors for both visible ($\lambda$= 630 nm) and infrared ($\lambda$= 1550 nm) photons when biased close to the critical current, with a dark count rate of <10 cps. $Mg{B}_2$ photodetectors over-perform NbN SNSPDs in speed by at least an order of magnitude for similar nanowire lengths. Such photodetectors offer a platform for single-photon detectors with a long thought-after combination of a large detector area and a response rate of up to 10 GHz with a single readout line.

11 pages, 4 figures, Supplementary Information of 4 pages and 3 figures