Weconsider a bipartite quantum system S = AB such that the part A is isolated from the environment E and onlythepartB interactswithE.Undersuchcircumstances,entanglementofthesystemmayexperiencedecreases and increases, during the evolution of the system. Here, we show that the entanglement of the system can exceed its initial value, under such local interaction, even though, at the initial moment, there is no entanglement in the environment and the system and the environment are only classically correlated. The case which is studied in this paper possesses another interesting feature too: The reduced dynamics of the system can be modeled as a completely positive map. In addition, we introduce the concept of inaccessible entanglement to explain why entanglement can exceed its initial value, under local interactions, in open quantum systems.

Keywords