1307.0363 (Francesco Buscemi)

Complete positivity in the presence of initial correlations: necessary
and sufficient conditions given in terms of the quantum data-processing
inequality    [PDF]

Francesco Buscemi

We provide here a complete characterisation of those initial system-environment correlations that always lead to completely positive reduced dynamics. This is done by showing that initial system-environment correlations always give rise to completely positive reduced dynamics if and only if the quantum data-processing inequality is never violated, i.e. if and only if a backward flow of information from the environment to the system cannot occur. Such condition is suitably modelled by short quantum Markov chains. The approach we propose, besides providing a new information-theoretic understanding of open system dynamics, clarify and unify previous approaches to the same problem.

View original: http://arxiv.org/abs/1307.0363