@PRL Sudden-change dynamics of quantum discord

Nonclassical correlations play a crucial role in the development of quantum information science. The recent discovery that nonclassical correlations can be present even in separable (nonentangled) states has broadened this scenario. This generalized quantum correlation has been increasing in relevance in several fields, among them quantum communication, quantum computation, quantum phase transitions, and biological systems. We demonstrate here the occurrence of the sudden-change phenomenon and immunity against some sources of noise for the quantum discord and its classical counterpart, in a room temperature nuclear magnetic resonance setup. The experiment is performed in a decohering environment causing loss of phase relations among the energy eigenstates and exchange of energy between system and environment, resulting in relaxation to the Gibbs ensemble.

Our original theoretical paper where the sudden-change phenomena was first identified: Physical Review A 80, 044102 (2009)

Our experimental observation in NMR: Phys. Rev. Lett. 107, 140403 (2011)].

Another observation in an optical system by Guang-Can Guo's group from China: Jin-Shi Xu, et al. Nature Communications 1, 7 (2010)