Entanglement Swapping with Independent Sources over an Optical Fibre Network

TL;DR

This paper reports a field-test experiment demonstrating entanglement swapping over an optical fibre network with independent sources, enabling secure quantum communication and key distribution.

Contribution

It presents the first field-test of entanglement swapping with independent sources over a city-scale optical fibre network.

Findings

Achieved a visibility of 79.9%, sufficient to violate Bell inequality.

Demonstrated source-independent quantum key distribution.

Validated the feasibility of quantum networks with independent entangled sources.

Abstract

Teleportation of an entangled state, known as entanglement swapping, plays an essential role in quantum communication and network.Here we report a field-test entanglement swapping experiment with two independent telecommunication band entangled photon-pair sources over the optical fibre network of Hefei city. The two sources are located at two nodes 12 km apart and the Bell-state measurement is performed in a third location which is connected to the two source nodes with 14.7 km and 10.6 km optical fibres. An average visibility of 79.9+/-4.8% is observed in our experiment, which is high enough to infer a violation of Bell inequality. With the entanglement swapping setup, we demonstrate a source independent quantum key distribution, which is also immune to any attack against detection in the measurement site.