Optical dynamics of cavity-integrated silicon colour centres

Synopsis

Distributed quantum computing requires the generation of high-fidelity entanglement between spatially separated qubits. Solid-state spin-photon interfaces offer a scalable route toward this goal due to their compatibility with nanophotonic integration and semiconductor fabrication. The silicon T centre is a promising candidate platform, combining native telecom-band emission with long electron and nuclear spin coherence in an isotopically purifiable host. However, the practical realization of remote entanglement protocols with this system is constrained by dynamics including spectral diffusion and imperfect optical cyclicity. This thesis presents the first investigation of these mechanisms in cavity-integrated T centres. We characterize spectral diffusion using two-colour correlation spectroscopy, revealing excitation induced charge reconfiguration in the local environment as the dominant source of frequency fluctuations in nanophotonic T centre devices. We find the dynamics are well described by an Ornstein-Uhlenbeck stochastic process, enabling extraction of a per-pulse reconfiguration rate. We further demonstrate a resonance-check photoluminescence excitation protocol that conditions optical excitation on spectral alignment, achieving a 35-fold narrowing of the effective linewidth from 3.8 GHz to 110 MHz. Modeling shows that such active conditioning can significantly accelerate multi-emitter entanglement generation. We analyze optical cyclicity through spin-resolved excited-state measurements and a model that decomposes spin preservation per excitation cycle into contributions from thermalization, laser-driven spin mixing, radiative branching, and non-radiative decay. We confirm excited-state thermalization follows a Boltzmann scaling and identify a temperature regime below T < 1.4 K in which thermal mixing is strongly suppressed. We observe laser-driven spin mixing that scales with excitation power and can be induced by off-resonant fields, consistent with a mechanism involving laser-driven fluctuating local electric fields. Direct measurements of radiative branching ratios and intrinsic cyclicity show that current performance is primarily limited by non-radiative decay. Together, these results establish quantitative performance benchmarks for silicon T centres in nanophotonic architectures and identify suppression of charge noise and non-radiative decay as critical steps toward scalable quantum network nodes.

For Zoom link info, please contact Lindiwe Coyne at physgrad@sfu.ca.