Experimental Synchronization of Independent Entangled Photon Sources
  Realistic linear quantum information processing necessitates the ability to synchronously generate entangled photon pairs either at the same or at distant locations. Here, we report the experimental realization of synchronized generation of independent entangled photon pairs. The quality of synchronization is confirmed by observing a violation of Bell's inequality with 3.2 standard deviations in an entanglement swapping experiment. The techniques developed in our experiment will be of great importance for future linear optical realization of quantum repeaters and quantum computation. 
Tao Yang, Qiang Zhang, Teng-Yun Chen, Shan Lu, Juan Yin, Jian-Wei Pan,   Zhi-Yi Wei, Jing-Rong Tian, and Jie Zhang