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

摘要： 利用诱骗态方法的测量设备无关的量子密钥分发可以避免不完美单光子源和探测器损耗带来的安全漏洞威胁.在实际应用的量子密钥分发中，增加传输距离和提高安全成码率是一个中心任务.报道了关于利用最优化的四强度诱骗态方法来演示测量设备无关的量子密钥分发MDIQKD的实验，其利用超低损耗光纤安全传输达到404km，利用标准光纤安全传输达到311km，在MDIQKD领域甚至所有类型的量子密钥分发中创造了新的安全传输记录.在相同实验条件下，传统BB84量子密钥分发协议即使利用完美的单光子源也不可能实现安全成码.该实验在证明和发展可行的长距离量子密钥分发取得了重要进步.

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