Extracting Information from Qubit-Environment Correlations

TL;DR

This paper reveals how the distribution of quantum correlations between qubits and their environment constrains entanglement and correlations in quantum systems, providing methods to optimize and analyze these correlations without full environment knowledge.

Contribution

It introduces a framework to analyze and optimize qubit correlations via qubit-environment information flow, emphasizing the importance of environment correlations in open quantum systems.

Findings

Optimizing interqubit correlations through qubit-environment information flow.

Relationship between early-stage qubit disentanglement and environment entanglement.

Qubit energy asymmetry can identify scenarios where qubit entanglement minima align with environment entanglement extrema.

Abstract

Most works on open quantum systems generally focus on the reduced physical system by tracing out the environment degrees of freedom. Here we show that the qubit distributions with the environment are essential for a thorough analysis, and demonstrate that the way that quantum correlations are distributed in a quantum register is constrained by the way in which each subsystem gets correlated with the environment. For a two-qubit system coupled to a common dissipative environment $\mathcal{E}$, we show how to optimise interqubit correlations and entanglement via a quantification of the qubit-environment information flow, in a process that, perhaps surprisingly, does not rely on the knowledge of the state of the environment. To illustrate our findings, we consider an optically-driven bipartite interacting qubit $AB$ system under the action of $\mathcal{E}$. By tailoring the light-matter interaction, a relationship between the qubits early stage disentanglement and the qubit-environment entanglement distribution is found. We also show that, under suitable initial conditions, the qubits energy asymmetry allows the identification of physical scenarios whereby qubit-qubit entanglement minima coincide with the extrema of the $A\mathcal{E}$ and $B\mathcal{E}$ entanglement oscillations.