Sudden Change of Quantum Discord under Single Qubit Noise
  We show that the sudden change of quantum correlation can occur even when only one part of the composite entangled state is exposed to a noisy environment. Our results are illustrated through the action of different noisy environments individually on a single qubit of quantum system. Composite noise on the whole of the quantum system is thus not the necessarily condition for the occurrence of sudden transition for quantum correlation. 
Li-Xing Jia, Bo Li, R.-H. Yue, and Heng Fan
quant-ph