Experimental realization of a quantum relay over a significant distance

A quantum teleportation over long distances is reported. Alice's unknown quantum state carried by a 1300 nm photon is teleported onto Bob's 1550 nm photon. Bob is situated in another lab connected with the EPR source by 2 km of optical fibres and at a physical distance of 55 m. The Bell state measurement is performed between two photons that travelled through 2 km of optical fibres each. This is a simulation of a transmission of a quantum state over 6 km using quantum teleportation which is the principle of a quantum relay protocol. A fidelity of 77% is obtained which is higher than the fidelity obtained with the best protocol using not entangled particles.