Future efforts to build quantum networks are likely to rely on the ability to interface and entangle disparate quantum systems. Two systems of interest in the realm of quantum information are trapped ions and Rydberg atoms. These systems operate at vastly different wavelengths so direct photonic interaction has been a challenge, however, establishing a photonic link would open the door to hybrid protocols leveraging the advantages of each system. Here, we demonstrate near perfect Hong-Ou-Mandel (HOM) interference between photons generated by a barium ion and a rubidium Rydberg ensemble, located in separate buildings and connected via an optical fibre. Our work serves as a building block for future hybrid ion-Rydberg quantum networks.
