测量设备无关量子密码与传统通信波分复用研究

Quantum key distribution (QKD) provides information-theoretically secure communication. However, in practice, QKD faces many restrictions in its development and generalization. On the one hand, many loopholes exist in realistic QKD systems. In particular, many hacking attacks exploit imperfections of the single-photon detection systems. The newly proposed measurement-device-independent QKD (MDIQKD) protocol can defeat all detector side channel attacks. On the other hand, in order to protect ultra-weak QKD signals, conventional QKD signals require a dedicated fiber link for transmission, thus substantially increasing the application costs. With the development of wavelength-division multiplexing technology, it is possible to integrate QKD with classical optical communications and reduce the cost of QKD. The focus of this project lies in the theoretical and experimental research for combining the MDIQKD protocol with the coexistence method based on wavelength-division multiplexing technology. The project aims at developing the technology for the interference of two independent lasers while multiplexing with classical optical communications, as well as the incorporation of MDIQKD with high efficiency gated single photon detectors, to achieve the coexistence of MDIQKD with classical optical communications over more than 100 km fiber link. This project will make an important contribution to the practical application and networking of loophole-free QKD.

量子密钥分发可以提供理论上无条件安全的保密通信。但在现实中，量子密钥分发的发展和推广受到许多限制。一方面，量子密钥分发系统存在诸多漏洞，其中单光子探测系统尤其容易受到各种攻击。近年来提出的测量设备无关的量子密钥分发协议，能够免疫所有针对探测系统的攻击。另一方面，由于量子密钥分发系统传输的量子信号强度十分弱，一般需要一根单独的光纤链路传输量子信号，这大大增加了应用成本。波分复用技术的发展使得量子密钥分发和经典光通信共享光纤资源成为可能，能降低量子密钥分发的成本。本项目拟研究将测量设备无关的量子密钥分发协议与传统通信波分复用技术结合的方法，计划发展遥远两地独立激光光源在与经典通信波分复用共纤传输时的干涉和高效融合超高灵敏度门控模式单光子探测两项技术，实现百公里以上的测量设备无关量子密钥分发协议与经典通信波分复用实验验证，为未来安全无漏洞的量子密钥分发技术的实用化、网络化推广将做出重要的贡献。

量子密钥分发利用量子物理基本原理，可为通信双方产生理论上无条件安全的随机密钥，保证了信息传输过程中的安全性。光子作为最普遍应用的信息载体，其传输损耗是量子密钥分发协议实现的主要障碍。如何克服传输损耗从提高密钥速率，传输距离是量子密钥分发协议理论和实验研究的核心任务。在应用推广上，如何降低设备成本和使用成本，是实验研究的主要内容。我们在世界上首次把光纤量子保密通信的安全距离拓展到500km以上，并把现场光纤的距离的世界记录从130km一下子提高到428km。如果把该技术应用到“量子通信京沪干线”上，可以把可信中继的数量减少一半以上。并且，可以实现所有的可信中继都布置在城市安保严格的重要机房之中，提高量子保密通信网络的管理安全。而基于10G-EPON 的量子接入网技术，解决了量子保密通信入户或者企业的最后一公里问题，不需要额外布置光纤，将为量子安全保障进入千家万户打下坚实的技术基础。