Time-invariant entanglement and sudden death of non-locality
  We investigate both theoretically and experimentally the dynamics of entanglement and non-locality for two qubits immersed in a global pure dephasing environment. We demonstrate the existence of a class of states for which entanglement is forever frozen during the dynamics, even if the state of the system does evolve. At the same time non-local correlations, quantified by the violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality, either undergo sudden death or are trapped during the dynamics. 
Bi-Heng Liu, Xiao-Min Hu, Jiang-Shan Chen, Chao Zhang, Yun-Feng Huang,   Chuan-Feng Li, Guang-Can Guo, G\"oktu\u{g} Karpat, ...
quant-ph