Reduced quantum dynamics with initial system-environment correlations characterized by pure Markov states
Any tripartite state which saturates the strong subadditivity relation for the quantum entropy is defined as the Markov state.A tripartite pure state describing an open system, its environment and their purifying system isa pure Markov state iff the bipartite marginal state of purifying system and environment is a product state. It has been shown that as long as the purification of the input system-environment state is a pure Markov state the reduced dynamics of the open system can be described, on the support of initial system state, by a quantum channel for every joint unitary evolution of the system-environment composite even in the presence of initial correlations. Entanglement, discord and classical correlations of the initial system-environment states implied by the pure Markov state are analyzed and it has been shown that all these correlations are entirely specified by the entropy of the environment. Some implications concerning perfect quantum error correction procedure and quantum Markovian dynamics are presented.