Sharing multi-partite quantum entanglement between parties allows for diverse secure communication tasks to be performed. Among them, conference key agreement (CKA), an extension of key distribution to multiple parties, has received much attention recently. Interestingly, CKA can also be performed in a way that protects the identities of the participating parties, therefore providing anonymity. In this work, we propose an anonymous CKA protocol for three parties that is implemented in a highly practical network setting. Specifically, a line of quantum repeater nodes is used to build a linear cluster state among all nodes, which is then used to anonymously establish a secret key between any three of them. The nodes need only share maximally entangled pairs with their neighbours, therefore avoiding the necessity of a central server sharing entangled states. This repeater setup makes our protocol an excellent candidate for implementation in future quantum networks. We explicitly prove that our protocol protects the identities of the participants from one another and perform an analysis of the key rate in the finite regime, contributing to the quest of identifying feasible quantum communication tasks for network architectures beyond point-to-point.

翻译：多方共享量子纠缠态可以实现多种安全通信任务。其中，会议密钥协议（CKA）作为密钥分发在多参与方场景的扩展，近年来受到广泛关注。值得注意的是，CKA可通过保护参与方身份的方式实现匿名性。本文提出一种三方匿名CKA协议，该协议在高度实用的网络环境中实现。具体而言，利用量子中继节点序列构建所有节点间的线性簇态，进而支持其中任意三方匿名建立共享密钥。节点仅需与相邻节点共享最大纠缠对，从而避免了中心服务器分发纠缠态的必要性。这种中继架构使我们的协议成为未来量子网络实现的优秀候选方案。我们明确证明了该协议能保护参与者之间的身份匿名性，并进行了有限密钥率分析，为探索超越点对点网络架构的可行量子通信任务提供了贡献。