Heralded distribution of atom-atom entanglement over metropolitan distance

A key challenge in the field of quantum information is to distribute entanglement over large distances. While photonic entanglement has been distributed over hundreds of kilometers, future quantum physics tests and applications require storing the entanglement faithfully in distant matter nodes. In my talk I will show our recent results regarding the heralded distribution of entanglement over two individual atoms separated by 14km. A photon qubit entangled with the sending atom node, travels over 24km of deployed fiber, and is stored in the receiving atom node while generating a herald signal. Low-noise quantum frequency conversion between the near-visible and the telecom bands at both the sending and receiving node laboratories enables an efficient and faithful propagation of the entangled photon over the metropolitan fiber link. We obtain a heralded atom-atom entangled state fidelity of F=0.78(2) and store the entanglement for more than 200μs, longer than the link communication time. Our atomic entanglement link opens the way for advanced quantum communication schemes over metropolitan distance and shows potential for scalability using further distant nodes.