On the 3rd, the reporter learned from the Jinan Institute of Quantum Technology that after the first experiment verified the feasibility of long-distance dual-field quantum key distribution and implemented the dual-field quantum key distribution experiment in a 300-kilometer real-world fiber, Jinan Quantum Technology Professor Wang Xiangbin and Researcher Liu Yang of the Research Institute collaborated with the team of academician Pan Jianwei of the University of Science and Technology of China once again to realize the dual-field quantum key distribution (TF-QKD) of 509 kilometers of real environment optical fiber. Related results have been published online in the international journal "Physical Review Letters" recently. Professor Wang Xiangbin and Professor Zhang Qiang are co-corresponding authors. This achievement successfully created a new world record for the longest transmission distance of quantum key distribution.
In the long-distance practical application of quantum key distribution (QKD), channel loss is the most serious limiting factor. TF-QKD uses single photon interference as an effective detection event, so that the safe code rate decreases linearly with the square root of the channel attenuation, and it can even easily break the linear limit of QKD code rate without relaying. However, the implementation conditions of TF-QKD are quite harsh, requiring single-photon-level interference of two remote independent lasers, and at the same time need to achieve accurate estimation of the relative phase shift of long-distance fiber links through the single-photon detection results.
The theoretical aspect of this achievement is based on the "send-not-send" dual-field quantum key distribution protocol proposed by Wang Xiangbin, which greatly improves the system's ability to tolerate phase noise. In the experimental aspect, Zhang Qiang's team adopted time-frequency transmission technology and used two independent remote lasers. The wavelength is locked to the same, and the additional phase reference light is used to estimate the relative phase drift of the fiber, which ensures the safety properties of the measurement device. Finally, the QKD safe coding distance was successfully extended to 509 kilometers in the laboratory, breaking the absolute theoretical coding rate limit defined by traditional non-relay QKD. At the same time, compared with other dual-field QKD experiments, this study has a unique advantage in security: it is not only measurement equipment-independent, but also fully considers the security under limited code length. If the system repetition frequency is upgraded to 1GHz used in long-distance quantum communication networks such as the Beijing-Shanghai main line, the code rate can reach 5kbps at 300 kilometers, which will greatly reduce the number of trusted relays in the backbone fiber optic quantum communication network. Greatly improve the security of optical fiber quantum secret communication network. (Reporter Wang Yanbin correspondent Zhan Chang Yan Tianshan)
ZHONGSHAN G-LIGHTS LIGHTING CO., LTD. , https://www.glightsled.com