Witness for initial system-environment correlations in open system dynamics

TL;DR

This paper investigates how initial correlations between a quantum system and its environment affect the system's evolution, revealing that distinguishability can increase and proposing a way to detect such correlations through measurements.

Contribution

It introduces a method to witness initial system-environment correlations by analyzing the growth of trace distance in open quantum systems.

Findings

Trace distance can increase beyond initial value due to initial correlations

Derived tight bounds for the growth of distinguishability in open systems

Proposed a measurement-based witness for initial correlations

Abstract

We study the evolution of a general open quantum system when the system and its environment are initially correlated. We show that the trace distance between two states of the open system can increase above its initial value, and derive tight upper bounds for the growth of the distinguishability of open system states. This represents a generalization of the contraction property of quantum dynamical maps. The obtained inequalities can be interpreted in terms of the exchange of information between the system and the environment, and lead to a witness for system-environment correlations which can be determined through measurements on the open system alone.