Attacking a practical quantum-key-distribution system with wavelength-dependent beam-splitter and multiwavelength sources
Hong-Wei Lia b, Shuang Wanga, Jingzheng Huanga, Wei Chena, Zhen−Qiang Yina, Fang-Yi Lia, Zheng Zhoua, Dong Liua, Yang Zhanga, Guang‐Can Guoa, Wan‐Su Baob, Zheng‐Fu Hana
- aKey Laboratory of Quantum Information,University of Science and Technology of China, Hefei, 230026, China
- bZhengzhou Information Science and Technology Institute, Zhengzhou, 450004, China
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Abstract
It is well known that the unconditional security of quantum-key distribution (QKD) can be guaranteed by quantum mechanics. However, practical QKD systems have some imperfections, which can be controlled by the eavesdropper to attack the secret key. With current experimental technology, a realistic beam splitter, made by fused biconical technology, has a wavelength-dependent property. Based on this fatal security loophole, we propose a wavelength-dependent attacking protocol, which can be applied to all practical QKD systems with passive state modulation. Moreover, we experimentally attack a practical polarization encoding QKD system to obtain all the secret key information at the cost of only increasing the quantum bit error rate from $1.3$ to $1.4%$.