关键词: 量子密钥分发, 测量设备无关, 诱骗态方案, 超低损耗光纤, 无条件安全通信

Abstract: Measurement device independent quantum key distribution (MDIQKD) with the decoystate method negates security threats of both the imperfect singlephoton source and detection losses. Lengthening the distance and improving the key rate of QKD are vital issues in practical applications of QKD. Herein, we report the results of MDIQKD over 404km of ultralowloss optical fiber and 311km of standard optical fiber while employing an optimized fourintensity decoystate method. This recordbreaking implementation of the MDIQKD method not only provides a new distance record for both MDIQKD and all types of QKD systems but also, more significantly, achieves a distance that the traditional BB84 QKD would not be able to achieve with the same detection devices even with ideal singlephoton sources. This work represents a significant step toward proving and developing feasible longdistance QKD.

Key words: quantum key distribution, measurement-device-independent, decoy-state method, ultralow-loss optical fiber, unconditional secure communication