Quantum defects in the solid state, also known as color centers, are promising platforms for quantum technologies. As solid-state objects, they can be integrated into devices in a scalable manner. As atomic systems, they have rich energy level structures and inter-level optical and spin transitions which allow for versatile, high fidelity control. In this thesis, we describe detailed studies of color centers in diamond through a combination of experimental characterization, materials engineering and first principle studies.
Most of the studies in this thesis are based on the neutral silicon vacancy centers (SiV0) in diamond, a novel color center which is inaccessible in undoped diamonds. We use Fermi level engineering via careful materials preparation or novel doping techniques to stabilize SiV0 with high efficiency. We demonstrate that SiV0 centers have long spin coherence times, and narrow, stable optical transitions at cryogenic temperatures, making it a suitable platform for quantum memory applications. With detailed excited state spectroscopy, we identify higher-lying bound exciton states in SiV0. We demonstrate optically detected magnetic resonance in SiV0 centers via resonant excitation through their bound exciton transitions and zero-phonon-line transitions. We isolate single SiV0 centers, and perform characterization on their optical and spin dynamics. We discuss materials characterization techniques and treatment methods to understand the variation of formation yield of SiV0 centers in boron doped diamonds.
The techniques developed for SiV0 centers are broadly applicable to other color centers. Towards the end of this thesis, we apply those experimental techniques to characterize a newly identified telecom O-band color center in diamond. We study the optical properties of the telecom color center using photoluminescence, absorption, and transient absorption spectroscopy. We discuss its prospective for quantum applications.