Zhang Sheng, Wu Yu-Kai, Li Chang, Jiang Nan, Pu Yun-Fei, Duan Lu-Ming
Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China.
Phys Rev Lett. 2022 Feb 25;128(8):080501. doi: 10.1103/PhysRevLett.128.080501.
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.
图态是一类重要的多体纠缠态。先前在线性光学量子信息方案中实验生成图态，特别是格林伯格 - 霍恩 - 泽林格（GHZ）态时，其效率相对于系统规模呈指数衰减，这限制了其在量子网络中的大规模应用。在此，我们展示了一种高效方案，利用长寿命原子量子存储器仅以多项式开销制备图态。我们在两个原子系综中异步生成原子 - 光子纠缠态，仅在双方都成功时才检索存储的原子激发，并进一步将它们投影到一个四光子GHZ态。我们测量了这个GHZ态的保真度，并进一步展示了其在违反贝尔型不等式和量子密码学中的应用。我们的工作展示了在大规模分布式系统中高效生成多体纠缠态的前景，这些纠缠态可应用于量子信息处理和计量学。
