# Entanglement increase from local interaction in the absence of initial quantum correlation in the environment and between the system and the environment

## TL;DR

This paper demonstrates that in a bipartite quantum system with local environment interaction, entanglement can increase beyond initial levels even without initial quantum correlations, explained via the concept of inaccessible entanglement.

## Contribution

It shows entanglement can surpass initial values under local interactions without initial quantum correlations, and introduces the concept of inaccessible entanglement.

## Key findings

- Entanglement can exceed initial levels during local interactions.
- Reduced system dynamics can be modeled as a completely positive map.
- Introduces the concept of inaccessible entanglement to explain entanglement increase.

## Abstract

We consider a bipartite quantum system S=AB such that the part A is isolated from the environment E and only the part B interacts with E. Under such circumstances, entanglement of the system may experience decreases 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.