Memory-based quantum communication can overcome the dis-tance limit by adopting either the approach of a quantum repeater[1]or a transportable quantum memory[2,3].Photonic quantum memories have been demonstrated with various physical systems,including single atoms inside optical cavities[4],atomic gases[5]and impurities in solids[6].As an emerging solid-state platform,rare-earth-ion doped solids have enabled optical quantum storage with remarkable performances[6-9].Moreover,the rare-earth-ion doped crystal,i.e.,Eu3+∶Y2SiO5,is currently the only candidate for a transportable photonic quantum memory,due to its hours-long optical storage times[3].Despite these remarkable achievements,rare-earth-ion doped crystals typically have birefringence and ani-sotropic absorption which make the storage of polarization-qubits become a great challenge.Pioneering works[10-13]have demon-strated polarization qubit storage based on the two-level atomic frequency comb(AFC)with a predetermined storage time.The only exception is the demonstration of the spin-wave AFC protocol in a Eu3+∶Y2SiO5 crystal in a double-pass configuration[14].Unfortu-nately,the achieved storage process fidelity(～76.2％)cannot sur-pass the maximum fidelity achievable with a classical measure-and-prepare strategy[12].What's more,the double-pass configu-ration could introduce unwanted losses,instabilities and complex-ities for practical applications.Here we demonstrate a spin-wave solid-state quantum memory for photonic polarization qubits using a single piece of crystal in a single-pass configuration which has a storage process fidelity of 91.9％±2.4％for single-photon level weak coherent pulses.

Ming Jin;You-Zhi Ma;Zong-Quan Zhou;Chuan-Feng Li;Guang-Can Guo

CAS Key Laboratory of Quantum Information,University of Science and Technology of China,Hefei 230026,China;CAS Center for Excellence in Quantum Information and Quantum Physics,University of Science and Technology of China,Hefei 230026,China

科学通报（英文版）

[1]Ming Jin;You-Zhi Ma;Zong-Quan Zhou;Chuan-Feng Li;Guang-Can Guo-.A faithful solid-state spin-wave quantum memory for polarization qubits)[J].科学通报（英文版）,2022(07):676-678

repeater,transportable,sotropic,Pioneering

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