Postselected Entanglement between Two Atomic Ensembles Separated by 12.5 km

作者：Xi-Yu Luo, Yong Yu, Jian-Long Liu, Mingyang Zheng, Chaoyang Wang, Bin Wang, Jun Li, Xiao Jiang, Xiu-Ping Xie, Qiang Zhang, Xiao‐Hui Bao, Jian-Wei Pan · 发表于：Physical Review Letters · 年份：2022 · DOI：10.1103/physrevlett.129.050503 · 被引用次数：67 · 研究领域：Quantum optics and atomic interactions、Quantum Information and Cryptography、Quantum Mechanics and Applications

Quantum internet gives the promise of getting all quantum resources connected, and it will enable applications far beyond a localized scenario. A prototype is a network of quantum memories that are entangled and well separated. In this Letter, we report the establishment of postselected entanglement between two atomic quantum memories physically separated by 12.5 km directly. We create atom-photon entanglement in one node and send the photon to a second node for storage via electromagnetically induced transparency. We harness low-loss transmission through a field-deployed fiber of 20.5 km by making use of frequency down-conversion and up-conversion. The final memory-memory entanglement is verified to have a fidelity of 90% via retrieving to photons. Our experiment makes a significant step forward toward the realization of a practical metropolitan-scale quantum network.