Classical and quantum correlations for two-mode coherent-state superposition

Quantum discord, a kind of quantum correlation, is defined as the mismatch between two quantum analogues of classically equivalent expressions of the mutual information. Distinguish classical and quantum correlations in quantum systems is therefore of both fundamental and practical importance. We investigate here the dynamics of classical and quantum correlations for two-mode coherent-state superposition in vacuum environment, which are known to be particularly useful for quantum information processing. By analytical and numerical analyzes we find that, contrary to what is usually stated in the literature, quantum discord under decoherence may exhibit sudden death and sudden birth phenomena, and we show also that the classical and quantum correlations vanish at infinite time. Moreover, the quantum discord may be less or more robust than entanglement against environment depending on different strength regimes of the optical fields of the two-mode coherent-state superposition.