Experimental Passive Round-Robin Differential Phase-Shift Quantum Key Distribution

TL;DR

This paper presents an experimental demonstration of a passive RRDPS QKD system capable of generating secure keys over 50 km with high error tolerance, improving robustness in noisy environments.

Contribution

It introduces and experimentally validates a passive RRDPS QKD scheme that tolerates higher error rates than traditional protocols like BB84.

Findings

Secure key generation over 50 km distance

Bit error rate tolerance up to 29%

Passive RRDPS system operates at 500 MHz

Abstract

In quantum key distribution (QKD), the bit error rate is used to estimate the information leakage and hence determines the amount of privacy amplification --- making the final key private by shortening the key. In general, there exists a threshold of the error rate for each scheme, above which no secure key can be generated. This threshold puts a restriction on the environment noises. For example, a widely used QKD protocol --- BB84 --- cannot tolerate error rates beyond 25%. A new protocol, round-robin differential phase shifted (RRDPS) QKD, essentially removes this restriction and can in principle tolerate more environment disturbance. Here, we propose and experimentally demonstrate a passive RRDPS QKD scheme. In particular, our 500 MHz passive RRDPS QKD system is able to generate a secure key over 50 km with a bit error rate as high as 29%. This scheme should find its applications in noisy environment conditions.