Abstract When developing a practical continuous-variable quantum key distribution (CVQKD), the detector is necessary at the receiver's side. We investigate the practical security of the CVQKD system with an unbalanced heterodyne detector. The results show that unbalanced heterodyne detector introduces extra excess noise into the system and decreases the lower bound of the secret key rate without awareness of the legitimate communicators, which leaves loopholes for Eve to attack the system. In addition, we find that the secret key rate decreases more severely with the increase in the degree of imbalance and the excess noise induced by the imbalance is proportional to the intensity of the local oscillator (LO) under the same degree of imbalance. Finally, a countermeasure is proposed to resist these kinds of effects.
Fund: Project supported by the National Natural Science Foundation of China (Grant No. 62001383) and the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2019JM-591).
Corresponding Authors:
Weiqi Liu, Chen He
E-mail: vickylwq1991@nwu.edu.cn;chenhe@nwu.edu.cn
Cite this article:
Lingzhi Kong(孔令志), Weiqi Liu(刘维琪), Fan Jing(荆凡), and Chen He(贺晨) Practical security analysis of continuous-variable quantum key distribution with an unbalanced heterodyne detector 2022 Chin. Phys. B 31 070303
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