The continuous-variable version of quantum key distribution (QKD) offers the advantages (over discrete-variable systems) of higher secret key rates in metropolitan areas as well as the use of standard telecom components that can operate at room temperature. An important step in the real-world adoption of continuous-variable QKD is the deployment of field tests over commercial fibers. Here we report two different field tests of a continuous-variable QKD system through commercial fiber networks in Xi'an and Guangzhou over distances of 30.02 km (12.48 dB) and 49.85 km (11.62 dB), respectively. We achieve secure key rates two orders-of-magnitude higher than previous field test demonstrations. This is achieved by developing a fully automatic control system to create stable excess noise and by applying a rate-adaptive reconciliation protocol to achieve a high reconciliation efficiency with high success probability. Our results pave the way to achieving continuous-variable QKD in a metropolitan setting.
@article{arxiv.1709.04618,
title = {Continuous-variable QKD over 50km commercial fiber},
author = {Yi-Chen Zhang and Zhengyu Li and Ziyang Chen and Christian Weedbrook and Yijia Zhao and Xiangyu Wang and Yundi Huang and Chunchao Xu and Xiaoxiong Zhang and Zhenya Wang and Mei Li and Xueying Zhang and Ziyong Zheng and Binjie Chu and Xinyu Gao and Nan Meng and Weiwen Cai and Zheng Wang and Gan Wang and Song Yu and Hong Guo},
journal= {arXiv preprint arXiv:1709.04618},
year = {2019}
}