Telecom-wavelength quantum relay using a semiconductor quantum dot

One promising technology expected to enable long-haul quantum communication networks with untrusted nodes are quantum relays. Their most practical implementation requires an entanglement source with operation at telecom wavelength and intrinsic single photon character. Here, we use a semiconductor quantum dot emitting in the O-band to demonstrate for the first time a system fulfilling both of these criteria. For implementation of a standard 4-state QKD-protocol with weak coherent input states, the system achieves mean fidelities above 88%. Further characterization of the relay with process tomography reveals teleportation for arbitrary input states. The results represent a significant advance in demonstrating feasibility of semiconductor light sources for the development of infrastructure-compatible quantum-communication technology for multi-node networks.