Zhang Haoran, Sun Zhen, Qi Ruoyang, Yin Liuguo, Long Gui-Lu, Lu Jianhua
State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, China.
Beijing Academy of Quantum Information Science, Beijing, China.
Light Sci Appl. 2022 Apr 6;11(1):83. doi: 10.1038/s41377-022-00769-w.
Rapid progress has been made in quantum secure direct communication in recent years. For practical application, it is important to improve the performances, such as the secure information rate and the communication distance. In this paper, we report an elaborate physical system design and protocol with much enhanced performance. This design increased the secrecy capacity greatly by achieving an ultra-low quantum bit error rate of <0.1%, one order of magnitude smaller than that of existing systems. Compared to previous systems, the proposed scheme uses photonic time-bin and phase states, operating at 50 MHz of repetition rate, which can be easily upgraded to over 1 GHz using current on-the-shelf technology. The results of our experimentation demonstrate that the proposed system can tolerate more channel loss, from 5.1 dB, which is about 28.3 km in fiber in the previous scheme, to 18.4 dB, which corresponds to fiber length of 102.2 km. Thus, the experiment shows that intercity quantum secure direct communication through fiber is feasible with present-day technology.
近年来，量子安全直接通信取得了快速进展。对于实际应用而言，提高诸如安全信息速率和通信距离等性能非常重要。在本文中，我们报告了一种精心设计的物理系统和协议，其性能有了显著提升。通过实现低于0.1%的超低量子比特错误率，该设计极大地提高了保密容量，比现有系统低一个数量级。与先前的系统相比，所提出的方案使用光子时间槽和相位态，重复率为50MHz，利用现有的现成技术可以轻松升级到超过1GHz。我们的实验结果表明，所提出的系统能够容忍更多的信道损耗，从之前方案中光纤长度约28.3公里对应的5.1dB，提高到对应光纤长度102.2公里的18.4dB。因此，实验表明，利用当今技术通过光纤进行城市间量子安全直接通信是可行的。
