One of the central goals in quantum information science is constructing a quantum network useful for quantum communication, sensing, and computation. Its realization crucially depends on efficient distribution of entanglement. A promising approach entails connecting quantum nodes via photons, which are naturally resilient against decoherence, and storing quantum bits in atomic memories; among which, solid state spin qubits in diamond are particularly promising candidates for memory storage in a quantum repeater network. However, experimental efforts thus far have been mainly stymied by the absence of efficient and scalable spin-photon interfaces. To address these challenges, we propose a photonic integrated circuit architecture with heterogeneously integrated emitter-nanocavity systems for faithfully transferring photonic qubits onto diamond color centers. This hybrid platform offers arbitrary photonic routing, phase stability, and reconfigurability to achieve high-fidelity and high-efficiency local and remote entanglement generation. Subsequently, we report our experimental efforts in realizing a cavity-enhanced optical interface with tin-vacancy centers in diamond and characterizing a heterogeneously integrated emitter-cavity system in a silicon nitride photonic integrated circuit. The on-chip components allow for additional control over both the spin and optical degrees of freedom necessary for achieving spin-photon entanglement. As an outlook, we discuss how the experimental results and ongoing efforts pave the path towards additional quantum network applications, such as realizing a quantum random access memory.

Kevin C. Chen is currently a PhD student in the MIT Quantum Photonics group. His research focuses on developing scalable quantum networking systems based on color centers in diamond and integrated photonics.