MSE PhD Prospectus Defense: Umut Yazlar

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MSE PhD Prospectus Defense: Umut Yazlar

TITLE: Strain-Tunable Silicon-Vacancy Centers in Diamond Nanophotonic Cavities for Quantum Networks

ADVISOR: Nikola Maksimovic (Physics, MSE)

COMMITTEE: Mikhail Lukin (Harvard University, Physics), Marko Lončar (Harvard University, Electrical Engineering and Applied Physics), Luca Dal Negro (ECE, MSE)

ABSTRACT: Quantum networks are designed to distribute entanglement between spatially separated quantum systems, enabling applications in secure communication, distributed quantum computing, and quantum-enhanced non-local sensing. Building a useful network node requires the integration of several demanding capabilities: long-lived quantum memories, high-fidelity operations, and an efficient interface between stationary matter qubits and flying photonic qubits. Silicon-vacancy (SiV) centers in diamond nanophotonic cavities are a promising solid-state platform for this purpose, combining optically addressable electronic spins, access to ²⁹Si nuclear-spin memory qubits, and cavity-enhanced light–matter interactions. This thesis introduces the relevant background in remote entanglement generation, cavity quantum electrodynamics (cQED), SiV centers in diamond nanophotonic cavities, and the nanofabrication methods used to realize integrated quantum devices. A major bottleneck to scaling this platform is the emitter-to-emitter variation of SiV optical transition frequencies. This inhomogeneous frequency distribution reduces remote-entanglement generation rates by requiring an additional lossy frequency-shifting stage, and it hinders the deterministic generation of indistinguishable photons from multiple emitters. To advance the SiV platform, this work develops a strain-tunable nanocavity design in which optical transition frequencies are controlled in situ through electrostatic actuation of diamond nanocavities. Using this approach, spin–photon entanglement is demonstrated between an SiV and a photonic qubit with a Bell-state fidelity of 86%, together with photon–nucleus entanglement between the photonic qubit and the ²⁹Si nuclear spin with a Bell-state fidelity of 79%, while actively controlling the SiV optical transition frequency. These results establish strain tuning as a practical route toward frequency-tunable SiV quantum network nodes and provide a pathway to significantly increasing SiV–SiV entanglement generation rates.