Amendable Gaussian channels:restoring entanglement via a unitary filter

TL;DR

This paper demonstrates that certain Gaussian quantum channels can have their entanglement-breaking effects reversed by a specific unitary filter, with practical experimental verification methods proposed.

Contribution

It introduces the concept of amendable Gaussian channels and identifies conditions and unitary operations that restore entanglement, advancing quantum communication techniques.

Findings

Existence of amendable Gaussian channels.

Unitary filters can prevent channels from being entanglement breaking.

Proposed realistic quantum optics experiments for verification.

Abstract

We show that there exist Gaussian channels which are amendable. A channel is amendable if when applied twice is entanglement breaking while there exists a unitary filter such that, when interposed between the first and second action of the map, prevents the global transformation from being entanglement breaking [Phys. Rev. A 86, 052302 (2012)]. We find that, depending on the structure of the channel, the unitary filter can be a squeezing transformation or a phase shift operation. We also propose two realistic quantum optics experiments where the amendability of Gaussian channels can be verified by exploiting the fact that it is sufficient to test the entanglement breaking properties of two mode Gaussian channels on input states with finite energy (which are not maximally entangled).