Breaking entanglement-breaking by classical correlations

TL;DR

This paper demonstrates that classical correlations in a joint environment can reactivate entanglement distribution between quantum systems, even when individual channels are entanglement-breaking, challenging previous assumptions about decoherence effects.

Contribution

It reveals that classical correlations in a combined environment can restore entanglement transmission, a phenomenon previously thought impossible with purely classical correlations.

Findings

Classical correlations can reactivate entanglement distribution.

Entanglement reactivation occurs with zero-discord, separable states.

The effect applies to systems of any Hilbert space dimension.

Abstract

The inevitable interaction between quantum systems and environment induces effects of decoherence which may be so strong as to destroy any initial entanglement between the systems, a phenomenon known as "entanglement breaking". Here we show the simplest examples where the combination of two entanglement-breaking channels into a joint correlated-noise environment reactivates the distribution of entanglement, with classes of entangled states which are perfectly transmitted from a middle station (Charlie) to two remote stations (Alice and Bob). Surprisingly, this reactivation is induced by the presence of purely-classical correlations in the joint environment, whose state is separable with zero discord. This paradoxical effect is proven for quantum systems with Hilbert spaces of any dimension, both finite and infinite.