Restoring broken entanglement by separable correlations

TL;DR

This paper demonstrates that separable correlations can restore entanglement broken by thermal noise in bosonic Gaussian channels, enabling the activation of distillable entanglement in both direct and indirect distribution schemes.

Contribution

It introduces a method for reactivating entanglement using separable correlations in noisy bosonic channels, applicable to both direct and entanglement swapping schemes.

Findings

Separable correlations can restore entanglement in noisy channels.

Restored entanglement can be sufficient for distillation.

Activation occurs in both direct and indirect distribution schemes.

Abstract

We consider two bosonic Gaussian channels whose thermal noise is strong enough to break bipartite entanglement. In this scenario, we show how the presence of separable correlations between the two channels is able to restore the broken entanglement. This reactivation occurs not only in a scheme of direct distribution, where a third party (Charlie) broadcasts entangled states to remote parties (Alice and Bob), but also in a configuration of indirect distribution which is based on entanglement swapping. In both schemes, the amount of entanglement remotely activated can be large enough to be distilled by one-way distillation protocols.