Holographic Storage of Biphoton Entanglement
  Coherent and reversible storage of multi-photon entanglement with a multimode quantum memory is essential for scalable all-optical quantum information processing. Although single photon has been successfully stored in different quantum systems, storage of multi-photon entanglement remains challenging because of the critical requirement for coherent control of photonic entanglement source, multimode quantum memory, and quantum interface between them. Here we demonstrate a coherent and reversible storage of biphoton Bell-type entanglement with a holographic multimode atomic-ensemble-based quantum memory. The retrieved biphoton entanglement violates Bell's inequality for 1 microsecond storage time and a memory-process fidelity of 98% is demonstrated by quantum state tomography. 
Han-Ning Dai, Han Zhang, Sheng-Jun Yang, Tian-Ming Zhao, Jun Rui,   You-Jin Deng, Li Li, Nai-Le Liu, Shuai Chen, Xiao-Hui Ba...
quant-ph