Coupling Nitrogen-Vacancy Centres in Diamond to a Grape Dimer Cavity

Efficient coupling between microwave fields and solid-state spins is essential in many quantum technology applications, such as spin-based magnetic field sensors or (room-temperature) masing devices. This thesis investigates the coupling of an ensemble of Nitrogen-Vacancy (NV) centre spins in nanodiamonds to a novel type of microwave resonator, consisting of dielectric spherical or ellipsoidal dimers, which exhibit high-intensity magnetic field hotspots due to morphological-dependent resonances. Specifically, the thesis explores the use of grapes as building blocks for those resonators. Numerical modelling was performed to demonstrate the formation of magnetic field hotspots in grape dimers. In parallel, nanodiamonds with NV spin ensembles were placed between actual grape dimers and optically detected magnetic resonance (ODMR) measurements were carried out for characterisation. In the presence of grape dimers, the magnetic field was estimated to be more than double compared to measurements without grape dimers. The demonstration of NV spins interacting with the magnetic field in the hotspot between grape dimers serves as an initial step in constructing precise and more efficient cavity resonators based on a spherical or ellipsoidal dielectric design. Such cavities may lead to a low-cost and more effective alternative to existing techniques.