Pan Jianwei and Zhang Qiang from the University of Science and Technology of China, together with Wang Xiangbin from Tsinghua University, Liu Yang from Jinan Institute of Quantum Technology, You Lixing and Zhang Weijun from the Shanghai Institute of Microsystems, Chinese Academy of Sciences, have realized 1002km point-to-point remote quantum key distribution in optical fibers by developing technologies such as low crosstalk phase reference signal control and extremely low noise single photon detectors, Not only has it set a world record for fiber optic relay free quantum key distribution distance, but it also provides a solution for high-speed backbone links in intercity quantum communication. The relevant research results were published in the international academic journal "Physical Review Letters" on May 25th. Quantum Key Distribution (QKD) is based on the fundamental principles of quantum mechanics, which enables secure key distribution between users, combined with a "one-time encryption" encryption method, to achieve the highest security of secure communication. However, the distance of quantum key distribution has always been limited by factors such as the inherent loss of communication fibers and detector noise. The Dual Field Quantum Key Distribution (TF-QKD) protocol utilizes the characteristics of single photon interference to elevate the relationship between coding rate and distance from the linear relationship of general quantum key distribution to the level of square root. Therefore, it can obtain coding distance far beyond that of general quantum key distribution schemes. In this work, the research team adopted the "send not send" dual field quantum key distribution protocol proposed by Wang Xiangbin et al., which can effectively improve the working distance of quantum key distribution systems under practical conditions. In order to achieve quantum key distribution over extremely long distances, the research team collaborated with Changfei Fiber and Cable Co., Ltd. to use ultra-low loss optical fibers based on "pure silica core" technology to achieve quantum channel optical fiber links below 0.16 dB/km. The Shanghai Institute of Microsystems, Chinese Academy of Sciences, has developed an extremely low noise superconducting single photon detector, which suppresses the dark counting caused by thermal radiation by multi-level filtering in the temperature range of 40 K and 2.2 K, reducing the noise of the single photon detector to 0.02 cps. The research team also developed a dual wavelength phase estimation scheme based on time division multiplexing, which avoids the influence of noise such as secondary Rayleigh scattering of reference light at the same wavelength and spontaneous Raman scattering of reference light at different wavelengths, and reduces the link noise to below 0.01 Hz. Figure 1: Schematic diagram of a long-distance quantum key distribution experimental system. Based on the development of the above technology, this work has achieved dual field quantum key distribution up to 1002 km, achieving a coding rate of 0.0034 bps. After optimizing the system parameters, a coding rate of 47.06 kbps was obtained at a fiber optic distance of 202 km, and at fiber optic distances of 300 km and 400 km, the coding rate obtained was improved by 6 orders of magnitude compared to the original "measurement device independent" quantum key distribution. This work not only verifies the feasibility of the dual field quantum key distribution scheme at extremely long distances, but also verifies that using this protocol can achieve high bit rate quantum key distribution at intercity optical fiber distances, making it suitable for use in intercity quantum communication backbone links. This work has received high praise from the reviewers, who believe that it is an extremely important progress in the field of quantum cryptography