Trapped ions are qubit standards in quantum information science because of their long coherence times and high fidelity entangling gates controlled with external fields. Scaling to very large dimensions may require the use of a modular architecture where trapped ions in separate ion trap modules are entangled using a photonic interface while ions in the same module are entangled using a phonon bus. We report the successful combination of these types of entanglement within and between two modules. We use fast optics to generate heralded remote entanglement between modules at rates exceeding 4 per second, faster than the experimentally measured decoherence rate of the remote entangled state.
The resource scaling in such a modular architecture is super-exponential in the ratio of the mean remote entanglement time to the entangled qubit coherence time, and trapped ions are the only experimental system to date where this ratio is small and the overhead is not forbidding.
Modular quantum networks may involve the use of different types of qubits to create a large scale network. Heralded entanglement between qubits using photon interference is a powerful tool to create entanglement within heterogeneous quantum systems. We experimentally demonstrate the entanglement of non-identical qubits by interfering distinguishable photons emitted from distinguishable trapped ions without significant loss of remote entanglement rate or fidelity.