Protocols for creating and distilling multipartite GHZ states with Bell pairs (pre-calculated data)

The distribution of high quality Greenberger-Horne-Zeilinger (GHZ) states is at the heart of many quantum communication tasks, ranging from extending the baseline of telescopes to secret sharing. They also play an important role in error-correction architectures for distributed quantum computation, where Bell pairs can be leveraged to create an entangled network of quantum computers. We investigate the creation and distillation of GHZ states out of non-perfect Bell pairs over quantum networks. In particular, we introduce an algorithm based on dynamic programming to optimize over a large class of protocols that create and purify GHZ states. All protocols considered use a common framework based on measurements of non-local stabilizer operators of the target state (i.e., the GHZ state), where each non-local measurement consumes another (non-perfect) entangled state as a resource. The new protocols outperform previous proposals for scenarios without decoherence and local gate noise, by reducing the resources required to make high quality GHZ states. Furthermore, the algorithms can be applied for finding protocols for any number of parties and any number of entangled pairs involved.

高质量格林伯格-霍恩-蔡林格（Greenberger-Horne-Zeilinger, GHZ）态的分发，是诸多量子通信任务的核心所在，其应用场景涵盖从拓展望远镜观测基线到秘密共享等多个领域。这类态在分布式量子计算的纠错架构中同样发挥着关键作用——在此类架构中，可借助贝尔对（Bell pairs）构建量子计算机的纠缠网络。本研究针对量子网络中基于非完美贝尔对的GHZ态制备与提纯问题展开探究。具体而言，我们提出一种基于动态规划的算法，可对一类制备并提纯GHZ态的协议进行优化。所有被考量的协议均采用统一框架：以目标态（即GHZ态）的非局域稳定子算符测量为基础，且每一次非局域测量都将消耗一份额外的非完美纠缠态作为资源。在无退相干与本地门噪声的场景中，新协议通过降低制备高质量GHZ态所需的资源开销，性能优于此前提出的各类方案。此外，该算法可用于求解任意参与方数量、任意纠缠对数量的协议设计问题。