Sub-Mbps key-rate continuous-variable quantum key distribution with local-local-oscillator over 100 km fiber

TL;DR

This paper reports an experimental demonstration of a high-speed, long-distance continuous-variable quantum key distribution system over 100 km fiber, achieving sub-Mbps key rates with advanced noise control and signal processing techniques.

Contribution

The work introduces a novel CV-QKD system with local local-oscillator, combining multiplexing and a data-assisted equalization algorithm to enhance transmission distance and key rate.

Findings

Secure key rate of 10.36 Mbps at 50 km

Secure key rate of 2.59 Mbps at 75 km

Secure key rate of 0.69 Mbps at 100 km

Abstract

We experimentally demonstrated a sub-Mbps key rate Gaussian-modulated coherent-state continuous-variable quantum key distribution (CV-QKD) over 100 km transmission distance. To efficiently control the excess noise, the quantum signal and the pilot tone are co-transmitted in fiber channel based on wide-band frequency and polarization multiplexing methods. Furthermore, a high-accuracy data-assisted time domain equalization algorithm is carefully designed to compensate the phase noise and polarization variation in low signal-to-noise ratio. The asymptotic secure key rate (SKR) of the demonstrated CV-QKD is experimentally evaluated to be 10.36 Mbps, 2.59 Mbps, and 0.69 Mbps over transmission distance of 50 km, 75 km, and 100 km, respectively. The experimental demonstrated CV-QKD system significantly improves transmission distance and SKR compared to the state-of-art GMCS CV-QKD experimental results, and shows the potential for long-distance and high-speed secure quantum key distribution.