Measurement-device-independent quantum key distribution (MDI-QKD) is a technique for quantum-secured communication that eliminates all detector side-channels, although is currently limited by implementation complexity and low secure key rates. Here, we introduce a simple and compact MDI-QKD system design at gigahertz clock rates with enhanced resilience to laser fluctuations—thus enabling free-running semiconductor laser sources to be employed without spectral or phase feedback. This is achieved using direct laser modulation, carefully exploiting gain-switching and injection-locking laser dynamics to encode phase-modulated time-bin bits. Our design enables secure key rates that improve upon the state of the art by an order of magnitude, up to 8 bps at 54 dB channel loss and 2 kbps in the finite-size regime for 30 dB channel loss. This greatly simplified MDI-QKD system design and proof-of-principle demonstration shows that MDI-QKD is a practical, high-performance solution for future quantum communication networks.

与测量设备无关的量子密钥分发（MDI-QKD）是一种用于量子安全通信的技术，它消除了所有检测器旁通道，尽管目前受到实现复杂性和低安全密钥率的限制。在这里，我们介绍了一种简单紧凑的MDI-QKD系统设计，其时钟速率为千兆赫兹，具有增强的对激光波动的适应性-因此，可以使用自由运行的半导体激光源，而无需频谱或相位反馈。这是通过使用直接激光调制来实现的，仔细地利用增益切换和注入锁定激光动力学来对相位调制的时间bin位进行编码。我们的设计实现了安全的密钥速率，该密钥速率在现有技术水平上提高了一个数量级，在54 dB的信道损耗下可达8 bps，而在有限尺寸的情况下对于30 dB的信道损耗可达2 kbps。