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.
@article{arxiv.1505.08076,
title = {Experimental Passive Round-Robin Differential Phase-Shift Quantum Key Distribution},
author = {Jian-Yu Guan and Zhu Cao and Yang Liu and Guo-Liang Shen-Tu and Jason S. Pelc and M. M. Fejer and Cheng-Zhi Peng and Xiongfeng Ma and Qiang Zhang and Jian-Wei Pan},
journal= {arXiv preprint arXiv:1505.08076},
year = {2015}
}