A continuous-variable quantum repeater protocol enhanced with multiplexing and thermal noise

Abstract

The continuous-variable quantum repeater (CVQR) plays a crucial role in continuous-variable quantum key distribution (CV-QKD). It can largely extend the security distance limit of CV-QKD. Currently, the majority of CVQR designs relies on the use of noiseless linear amplifiers for entanglement distillation. However, practical noiseless linear amplifiers may reduce communication performances and suffer from low success rates due to the truncation noise produced during the amplification. To solve these problems, we propose an improved CVQR protocol assisted by mode multiplexing and thermal noises. The results show the advantage of our protocol: at 100 km, the success probability of our protocol is 0.4330, while that of the original protocol is 0.1390; the key rate under the collective attack is 0.0208 bits/pulse in our protocol, while that of the original protocol is 7.624e\(-\)06 bits/pulse at 500 km. The CVQR protocol proposed in this work paves the way for long-distance CV-QKD.