Nonlocality and robustness in two-photon entangled system

High-quality polarized two-photon entangled states were prepared by nonlinear parametric type II down-conversion and post-polarization selection methods. Clauser-Horne-Shimony-Holt (CHSH) and Cavalcanti were experimentally measured in a two-photon entanglement system. -Bell (CB) inequality violates the local realism. The values of CHSH and CB inequalities are 2.64±0.021 and 2.75±0.019 respectively. The bit-flip noise in the quantum channel is simulated by linear optics. The CHSH type is experimentally studied. The robustness of the inequality in the bit-flip noise environment shows that the CB is more robust than the CHSH inequality in the bit-flip noise environment, which provides experimental support for further research on the application of entanglement in quantum information processing.