Distance growth of quantum states due to initial system--environment correlations

TL;DR

This paper investigates how initial correlations between a quantum system and its environment can cause the distinguishability between quantum states to grow over time, challenging typical assumptions of contractive dynamics.

Contribution

It demonstrates that initial system-environment correlations can significantly increase the distance between quantum states, revealing a breakdown of the usual contractivity in non-Markovian dynamics.

Findings

Initial correlations can substantially increase quantum state distinguishability.

Distance contractivity can break down due to initial correlations.

Exact non-Markovian dynamics show long-term effects of initial correlations.

Abstract

Intriguing features of the distance between two arbitrary states of an open quantum system are identified that are induced by initial system-environment correlations. As an example, we analyze a qubit dephasingly coupled to a bosonic environment. Within tailored parameter regimes, initial correlations are shown to substantially increase a distance between two qubit states evolving to long-time limit states according to exact non-Markovian dynamics. It exemplifies the breakdown of the distance contractivity of the reduced dynamics.