Non-Markovianity through flow of information between a system and an environment

TL;DR

This paper explores the role of information exchange in non-Markovian quantum dynamics, introducing new measures based on quantum loss and accessible information, supported by theoretical analysis and experimental validation.

Contribution

It introduces a novel framework using quantum loss and accessible information to quantify information flow and non-Markovianity in open quantum systems, extending previous models.

Findings

Quantum loss relates closely to non-Markovianity measures.

Accessible information effectively quantifies information backflow.

Experimental results validate the theoretical measures.

Abstract

Exchange of information between a quantum system and its surrounding environment plays a fundamental role in the study of the dynamics of open quantum systems. Here we discuss the role of the information exchange in the non-Markovian behavior of dynamical quantum processes following the decoherence approach, where we consider a quantum system that is initially correlated with its measurement apparatus, which in turn interacts with the environment. We introduce a new way of looking at the information exchange between the system and environment using the quantum loss, which is shown to be closely related to the measure of non-Markovianity based on the quantum mutual information. We also extend the results of [Phys. Rev. Lett. 112, 210402 (2014)] by Fanchini et al. in several directions, providing a more detailed investigation of the use of the accessible information for quantifying the backflow of information from the environment to the system. Moreover, we reveal a clear conceptual relation between the entanglement and mutual information based measures of non-Markovianity in terms of the quantum loss and accessible information. We compare different ways of studying the information flow in two theoretical examples. We also present experimental results on the investigation of the quantum loss and accessible information for a two-level system undergoing a zero temperature amplitude damping process. We use an optical approach that allows full access to the state of the environment.