Experimental distribution of entanglement with separable carriers

TL;DR

This paper experimentally demonstrates that entanglement can be distributed between parties using a separable carrier photon, which is resilient to noise and can be the only method in noisy environments, advancing quantum networking capabilities.

Contribution

It provides the first experimental evidence that entanglement can be distributed via a carrier that remains unentangled, highlighting a novel method for quantum communication.

Findings

Entanglement can be generated without direct transfer of entangled particles.

Distributing entanglement with separable carriers is robust against noise.

This method can be essential in noisy quantum communication environments.

Abstract

The key requirement for quantum networking is the distribution of entanglement between nodes. Surprisingly, entanglement can be generated across a network without direct transfer - or communication - of entanglement. In contrast to information gain, which cannot exceed the communicated information, the entanglement gain is bounded by the communicated quantum discord, a more general measure of quantum correlation that includes but is not limited to entanglement. Here, we experimentally entangle two communicating parties sharing three initially separable photonic qubits by exchange of a carrier photon that is unentangled with either party at all times. We show that distributing entanglement with separable carriers is resilient to noise and in some cases becomes the only way of distributing entanglement through noisy environments.