Multiplexed entanglement of multi-emitter quantum network nodes

Quantum networks that distribute entanglement among remote nodes will unlock transformational technologies in quantum computing, communication and sensing^1-4. However, state-of-the-art networks^5-14 use only a single optically addressed qubit per node; this constrains both the quantum communication bandwidth and memory resources, greatly impeding scalability. Solid-state platforms^15-24 provide a valuable resource for multiplexed quantum networking in which multiple spectrally distinguishable qubits can be hosted in nano-scale volumes. Here we harness this resource by implementing a two-node network consisting of several rare-earth ions coupled to nanophotonic cavities^25-31. This is accomplished with a protocol that entangles distinguishable ¹⁷¹Yb ions through frequency-erasing photon detection combined with real-time quantum feedforward. This method is robust to slow optical frequency fluctuations occurring on timescales longer than a single entanglement attempt: a universal challenge amongst solid-state emitters. We demonstrate the enhanced functionality of these multi-emitter nodes in two ways. First, we mitigate the bottlenecks to the entanglement distribution rate through multiplexed entanglement of two remote ion pairs^32,33. Second, we prepare multipartite W-states comprising three distinguishable ions as a resource for advanced quantum networking protocols^34,35. These results lay the groundwork for scalable quantum networking based on rare-earth ions.