Experimental realization of three-color entanglement at optical fiber   communication and atomic storage wavelengths
  Multi-color entangled states of light including low-loss optical fiber transmission and atomic resonance frequencies are essential resources for future quantum information network. We present the experimental achievement on the three-color entanglement generation at 852 nm, 1550 nm and 1440 nm wavelengths for optical continuous variables. The entanglement generation system consists of two cascaded non-degenerated optical parametric oscillators (NOPOs). The flexible selectivity of nonlinear crystals in the two NOPOs and the tunable property of NOPO provide large freedom for the frequency selection of three entangled optical beams, so the present system is possible to be developed as practical devices used for quantum information networks with atomic storage units and long fiber transmission lines. 
Xiaojun Jia, Zhihui Yan, Zhiyuan Duan, Xiaolong Su, Hai Wang, Changde   Xie and Kunchi Peng
quant-ph physics.optics