论文标题
非局部图状态的量子内存增强制备
Quantum-Memory-Enhanced Preparation of Nonlocal Graph States
论文作者
论文摘要
图状态是一类重要的多部分纠缠状态。以前的实验生成图形状态，尤其是线性光学量子信息方案中的Greenberger-Horne-Zeilinger（GHz）态在效率方面经历了指数衰减与系统大小的指数衰减，这限制了其在量子网络中的大规模应用。在这里，我们证明了一种有效的方案，仅使用长期使用的原子量子记忆来准备只有多项式开销的图形状态。我们在两个原子集合中产生原子 - 孔子纠缠状态，仅在双方成功时才能检索存储的原子激发，并将它们进一步投射到四个photon GHz状态。我们衡量了该GHz状态的忠诚度，并进一步证明了其在违反贝尔型不平等和量子密码学方面的应用。我们的工作证明了在大规模分布式系统中有效生成多部分纠缠状态的前景，并在量子信息处理和计量学中应用。
Graph states are an important class of multipartite entangled states. Previous experimental generation of graph states and in particular the Greenberger-Horne-Zeilinger (GHZ) states in linear optics quantum information schemes is subjected to an exponential decay in efficiency versus the system size, which limits its large-scale applications in quantum networks. Here we demonstrate an efficient scheme to prepare graph states with only a polynomial overhead using long-lived atomic quantum memories. We generate atom-photon entangled states in two atomic ensembles asynchronously, retrieve the stored atomic excitations only when both sides succeed, and further project them into a four-photon GHZ state. We measure the fidelity of this GHZ state and further demonstrate its applications in the violation of Bell-type inequalities and in quantum cryptography. Our work demonstrates the prospect of efficient generation of multipartite entangled states in large-scale distributed systems with applications in quantum information processing and metrology.
