title: Quantum storage of orbital angular momentum entanglement in an atomic ensemble.
abstract: Constructing a quantum memory for a photonic entanglement is vital for realizing quantum communication and network. Because of the inherent infinite dimension of orbital angular momentum (OAM), the photon's OAM has the potential for encoding a photon in a high-dimensional space, enabling the realization of high channel capacity communication. Photons entangled in orthogonal polarizations or optical paths had been stored in a different system, but there have been no reports on the storage of a photon pair entangled in OAM space. Here, we report the first experimental realization of storing an entangled OAM state through the Raman protocol in a cold atomic ensemble. We reconstruct the density matrix of an OAM entangled state with a fidelity of 90.3%±0.8% and obtain the Clauser-Horne-Shimony-Holt inequality parameter S of 2.41±0.06 after a programed storage time. All results clearly show the preservation of entanglement during the storage.
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Dong-Sheng
authors.initials: DS
authors.lastname: Ding
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Zhi-Yuan
authors.initials: ZY
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Shi
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Guo-Yong
authors.initials: GY
authors.lastname: Xiang
authors.affiliation: State Key Laboratory of Fire Science, University of Science & Technology of China, Hefei, Anhui 230026, China.
authors.forename: Xi-Shi
authors.initials: XS
authors.lastname: Wang
authors.affiliation: College of Physics and Information Engineering, Fuzhou University, Fuzhou 350002, People's Republic of China.
authors.forename: Yun-Kun
authors.initials: YK
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Bao-Sen
authors.initials: BS
authors.lastname: Shi
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Guang-Can
authors.initials: GC
authors.lastname: Guo