Quantum conference key agreement is an important cryptographic primitive for future quantum network. Realizing this primitive requires high-brightness and robust multiphoton entanglement sources, which is challenging in experiment and unpractical in application because of limited transmission distance caused by channel loss. Here we report a measurement-device-independent quantum conference key agreement protocol with enhanced transmission efficiency over lossy channel. With spatial multiplexing nature and adaptive operation, our protocol can break key rate bounds on quantum communication over quantum network without quantum memory. Compared with previous work, our protocol shows superiority in key rate and transmission distance within the state-of-the-art technology. Furthermore, we analyse the security of our protocol in the composable framework and evaluate its performance in the finite-size regime to show practicality. Based on our results, we anticipate that our protocol will play an indispensable role in constructing multipartite quantum network.

翻译：量子会议密钥协商是未来量子网络中的重要密码原语。实现该原语需要高亮度且鲁棒的多光子纠缠源，这在实验中具有挑战性，且因信道损耗导致的传输距离受限而难以实际应用。本文提出一种测量设备无关的量子会议密钥协商协议，可在有损信道上提升传输效率。通过空间复用特性与自适应操作，我们的协议能够突破量子网络中无需量子存储的量子通信密钥率界限。与先前工作相比，我们的协议在现有技术水平下展现出密钥率和传输距离方面的优越性。进一步地，我们在可组合框架下分析了协议的安全性，并评估了有限码长条件下的性能以证明其实用性。基于上述结果，我们预期该协议将在构建多方量子网络中发挥不可或缺的作用。