Parallelizing single-photon detection for ultra-fast quantum key distribution

Häußler, Matthias;Beutel, Fabian;Gehring, Helge;Stegmüller, Robin;Walter, Nicolai;Wolff, Martin A.;Hartmann, Wladick;Tillmann, Max;Wahl, Michael;Röhlicke, Tino;Bülter, Andreas;Wernicke, Doreen;Perlot, Nicolas;Rödiger, Jasper;Pernice, Wolfram H.P.;Schuck, Carsten

Abstract

Quantum key distribution (QKD) protocols use photon states to transmit information, offering the potential for secure communication over vast distances. However, there's a challenge: even in low-loss optical fibers, the attenuation of optical signals over extended distances restricts the secret key rates to just a few kbit/s. To address this limitation, we've taken a novel approach. We've parallelized established quantum cryptography schemes across a greater number of channels. Our method employs arrays of individually addressable, low-noise, waveguide-integrated superconducting nanowire single-photon detectors. These detectors are pivotal in enabling ultra-fast QKD. Some key features of our detectors include: They operate at a temperature of 3 K. They boast detection efficiencies of up to 50%. They have dark count rates that are below 100 Hz. They offer a timing accuracy of up to 100 ps. Additionally, their compact design is highly advantageous. It facilitates the integration of both passive and active nanophotonic devices on a single chip. This includes components like delay lines, wavelength filters, and phase modulators.