发表机构
Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University; Electrical Engineering and Computer Science Department, Technische Universität Berlin; Dahlem Center for Complex Quantum Systems, Freie Universität Berlin（赫瑞瓦特大学工程与物理科学学院光子与量子科学研究所; 柏林工业大学电气与计算机科学系; 柏林自由大学达勒姆复杂量子系统中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文实验验证了具有可组合安全性的离散变量(n,n)阈值量子秘密共享协议，利用纠缠光子源生成4量子比特GHZ态，在20公里光纤网络中实现高速率秘密共享，并给出有限密钥下界。
AI 中文摘要
未来的量子通信网络将有望支持需要两个以上用户之间纠缠的密码任务。量子秘密共享是一个典型的例子，其中纠缠提供了一种直接的手段来协调不可信方，并在多方设置中防止窃听。然而，典型的基于GHZ的协议可能容易受到参与者攻击，即不可信的方试图在不合作的情况下获知秘密。在这里，我们实验评估了一个离散变量$(n,n)$-阈值量子秘密共享协议，其有限密钥分析提供了针对一般攻击（包括参与者攻击）的可组合安全性。利用两个域工程化的纠缠光子对源，我们以每秒超过$5\times10^3$个四重事件的速率生成4量子比特GHZ态，最大渐近秘密密钥率为每秒$750 \pm 10$比特。然后，我们通过一个总长度为20公里光纤的4臂星形网络分发该态。根据测量的事件率和误差统计，我们推断，在测量源和设备统计保持平稳的假设下，采用优化基选择概率的随机24小时执行将产生8.7 M比特的可组合有限密钥下界。
英文摘要
Future quantum communication networks will conceivably support cryptographic tasks that require entanglement among more than two users. Quantum secret sharing is a prime example where entanglement provides a direct means to coordinate untrusted parties with security from eavesdropping in a multi-party setting. However, the canonical GHZ-based protocols can be vulnerable to participant attacks, in which untrusted parties try to learn the secret without collaborating. Here, we experimentally evaluate a discrete-variable $(n,n)$-threshold quantum secret-sharing protocol whose finite-key analysis provides composable security against general attacks, including participant attacks. Using two domain-engineered entangled photon pair sources, we generate 4-qubit GHZ states at rates above $5\times10^3$ fourfold events per second and a maximum asymptotic secret key rate of $750 \pm 10$ bits per second. We then distribute the state through a 4-arm star network comprising 20km of fibre in total. From the measured event rates and error statistics, we infer that a randomised 24-hour execution with the optimised basis probability would yield a composable finite-key lower bound of 8.7 Mbits, under the assumption that the measured source and device statistics remain stationary.
Comments10 pages, 8 figures, letter
