Superconducting nanowire single photon detectors for quantum information and communications

TL;DR

This paper presents a practical six-channel superconducting nanowire single photon detector system operating at cryogenic temperatures, demonstrating its effectiveness in quantum key distribution and entanglement experiments for quantum communication.

Contribution

Developed a compact, cryogen-free six-channel SSPD system with high detection efficiency and stability for quantum information applications.

Findings

Detection efficiency of 2.6% at 1550 nm

Detection efficiency of 4.5% at 1310 nm

Successful field testing in quantum key distribution

Abstract

Superconducting nanowire single photon detectors (SNSPD or SSPD) are highly promising devices in the growing field of quantum information and communications technology. We have developed a practical SSPD system with our superconducting thin films and devices fabrication, optical coupling packaging, and cryogenic technology. The SSPD system consists of six-channel SSPD devices and a compact Gifford-McMahon (GM) cryocooler, and can operate continuously on 100 V ac power without the need for any cryogens. The SSPD devices were fabricated from high-quality niobium nitride (NbN) ultra-thin films that were epitaxially grown on single-crystal MgO substrates. The packaged SSPD devices were temperature stabilized to 2.96 K +/- 10 mK. The system detection efficiency for an SSPD device with an area of 20x20 $\mu m^2$ was found to be 2.6% and 4.5% at wavelengths of 1550 and 1310 nm, respectively, at a dark count rate of 100 c/s, and a jitter of 100 ps full width at half maximum (FWHM). We also performed ultra-fast BB84 quantum key distribution (QKD) field testing and entanglement-based QKD experiments using these SSPD devices.