Experiments with the negatively charged nitrogen vacancy (N
V−) in diamond highlight this defect's promise for coherent storage of quantum information. They have also spurred investigations of other color centers in diamond formed by defects that consist of Group IV element (Si, Ge, Sn, Pb) and vacancies which have different atomic structure than the N
V− center. To date, these other color centers have not exhibited coherence quite as impressive as that of the N
V− center. Spectral diffusion and the low Debye-Waller factor are important limitations of the N
V− center that make investigation of the other color centers necessary to advance the field. In this work we use density-functional theory (DFT) to study the thermodynamics and kinetics associated with the N
V, Si
V, Ge
V, Sn
V and Pb
V color centers in diamond. We find agreement between our theoretical calculations and the charge state of various color centers as observed in intrinsic diamond. We determine the Fermi level values that enhance the production of isolated color centers, which may lead to longer coherence times than their present values.
Realization of physical systems for quantum information processing fundamentally rests on the ability to generate entanglement among many quantum bits. To this end, solid state quantum systems are often considered a scalable approach due to the relative ease of generating of a large number of individual qubits. However, realizing strong coherent interactions that dominate decoherence processes in the solid state environment is a formidable challenge that has continued to motivate the investigation of new physical systems to store quantum information and new mechanisms to achieve controllable interactions. This thesis takes steps in these directions with diamond color centers, which can store optically accessible quantum information in their electronic spin. We study color center spins as acoustic two level systems, and consider whether their interaction with single phonons in diamond can be engineered to be coherent. Through spectroscopy of color centers in diamond nanomechanical devices and follow-up theoretical work, we identify the negatively charged silicon vacancy (SiV) color center as a promising candidate for phonon-mediated quantum information processing. In the process, an electromechanical device platform capable of tuning the strain environment of color centers is developed. It is used to mitigate thermal decoherence of the SiV spin and demonstrate photon-mediated quantum interference between two SiV centers on a diamond chip, highlighting the utility of nanomechanical devices for photonic quantum networks. Finally, we present high quality factor, wavelength scale acoustic resonators in diamond using phononic crystals towards a coherent interface between SiV centers and single phonons.