Revival of quantum correlations without system-environment back-action

TL;DR

This paper demonstrates that quantum correlations such as entanglement and discord can revive in a system of two qubits interacting with classical environments without back-action, challenging traditional views on environment-induced decoherence.

Contribution

It introduces a model where quantum correlations revive without back-action, linking revivals to classical-quantum correlations and non-Markovianity, expanding understanding of quantum system dynamics.

Findings

Quantum correlations can revive without back-action.

Classical environments can store and revive entanglement.

Revival linked to increased non-Markovianity parameter.

Abstract

Revivals of quantum correlations have often been explained in terms of back-action on quantum systems by their quantum environment(s). Here we consider a system of two independently evolving qubits, each locally interacting with a classical random external field. The environments of the qubits are also independent, and there is no back-action on the qubits. Nevertheless, entanglement, quantum discord and classical correlations between the two qubits may revive in this model. We explain the revivals in terms of correlations in a classical-quantum state of the environments and the qubits. Although classical states cannot store entanglement on their own, they can play a role in storing and reviving entanglement. It is important to know how the absence of back-action, or modelling an environment as classical, affects the kind of system time evolutions one is able to describe. We find a class of global time evolutions where back-action is absent and for which there is no loss of generality in modelling the environment as classical. Finally, we show that the revivals can be connected with the increase of a parameter used to quantify non-Markovianity of the single-qubit dynamics.