A fast and versatile quantum key distribution system with hardware key distillation and wavelength multiplexing

TLDR

The authors present a compact, 625 MHz coherent one‑way QKD system that continuously distributes secret keys over a single optical fibre, enabled by a fast hardware key‑distillation engine achieving up to 4 Mbps in real time. The system uses wavelength‑multiplexed coherent signals on a single fibre, with a 625 MHz clock and fast hardware key‑distillation, and is optimized for finite‑key security, authentication, and error rates (εQKD = 4 × 10⁻⁹). Secret keys were reliably distributed at rates above 21 kbps over 25 km of fibre using fast gated InGaAs single‑photon detectors.

Abstract

We present a compactly integrated, 625 MHz clocked coherent one-way quantum key distribution system which continuously distributes secret keys over an optical fibre link. To support high secret key rates, we implemented a fast hardware key distillation engine which allows for key distillation rates up to 4 Mbps in real time. The system employs wavelength multiplexing in order to run over only a single optical fibre. Using fast gated InGaAs single photon detectors, we reliably distribute secret keys with a rate above 21 kbps over 25 km of optical fibre. We optimized the system considering a security analysis that respects finite-key-size effects, authentication costs and system errors for a security parameter of εQKD = 4 × 10−9.