Non-Markovian Reactivation of Quantum Relays

TL;DR

This paper demonstrates that non-Markovian, correlated Gaussian noise can reactivate quantum protocols in a relay even after entanglement loss, with experimental validation showing potential benefits for quantum networks.

Contribution

It introduces a non-Markovian model for quantum relays that enables reactivation of quantum protocols through environmental noise correlations, a novel approach in quantum communication.

Findings

Protocols can be reactivated despite entanglement loss.

Correlated Gaussian noise can restore quadripartite entanglement.

Experimental proof confirms theoretical predictions.

Abstract

We consider a quantum relay which is used by two parties to perform several continuous-variable protocols: Entanglement swapping, distillation, quantum teleportation, and quantum key distribution. The theory of these protocols is extended to a non-Markovian model of decoherence characterized by correlated Gaussian noise. Even if bipartite entanglement is completely lost at the relay, we show that the various protocols can progressively be reactivated by the separable noise-correlations of the environment. In fact, above a critical amount, these correlations are able to restore the distribution of quadripartite entanglement, which can be localized into an exploitable bipartite form by the action of the relay. Our findings are confirmed by a proof-of-principle experiment and show the potential advantages of non-Markovian effects in a quantum network architecture.