Multipartite Mixed-Species Entanglement over a Quantum Network

We generate multipartite entangled states of two, three, and four matter qubits, where the entanglement is distributed over macroscopic distances via a photonic network link. Trapped-ion ^{88}Sr^{+} qubits are entangled directly via an optical fibre link, and the entanglement is subsequently extended to ^{43}Ca^{+} memory qubits cotrapped in each network node, using local mixed-species logic gates. We create remotely entangled Sr^{+}-Ca^{+} and Ca^{+}-Ca^{+} states, as well as mixed-species Greenberger-Horne-Zeilinger (GHZ) states of up to four qubits. We demonstrate storage of the remotely entangled memory qubits for ∼10  s, more than 100× the state creation time.