Hybrid atom — rare-earth ion quantum interfaces and network nodes

Future global quantum networks will merge heterogeneous quantum systems to simultaneously perform multiple tasks; namely, reliably store, process, and transmit quantum information as well as distribute entanglement. The functionality of such networks relies crucially on coherent interfaces between disparate, distant nodes, and telecom photons which connect them through low-loss optical fibers. We propose a modular hybrid network architecture composed of a pair of nodes with matching telecom wavelengths to circumvent loss due to quantum frequency conversion processes. On one side, atom-based nodes, including a warm atomic ensemble and an atom-array – nanophotonic cavity system, serve as our photon source node and processor node respectively, compatible with each other and capable of generating atom-photon entanglement. On the other side, a rare-earth ion-doped crystal serves as our memory node, where inhomogeneous broadening allows broadband and multiplexed storage for time-bin photonic qubits, creating entanglement between the hybrid nodes.

In this talk, we will present our results identifying mode-matching conditions between a rubidium vapor, our source, and an erbium-doped crystal, our memory. We will show experimental progress towards a fully functioning module: the former outputs a heralded telecom single photon via phase-matched four-wave mixing, and the latter coherently stores the photon via the atomic frequency comb protocol, preserving the non-classical correlation between the photon and its heralding pair. We will further discuss the outlook on integrating both elements with nanophotonics for distributed quantum computing, and deterministic entanglement distribution across a metropolitan area.