Diamond consists of a regular array or a lattice of carbon atoms as well as an extremely small number of defects in the carbon lattice, including impurities, such as nitrogen or silicon atoms, and vacancies - places in the lattice where atoms are missing. Suitable combinations of impurities and vacancies can lead to the formation of color centers, which interact with light and give color to an otherwise transparent diamond. A special color center is a “silicon-vacancy”, which consists of two adjacent vacancies with a silicon atom inserted in between. An electron trapped in such a color center can serve as a “quantum bit” or a qubit - fundamental unit of quantum information. An outstanding challenge for using these qubits to develop solid-state quantum computers is to mediate and precisely control the interactions between the qubits. This experimental program couples silicon vacancy qubits to the compressional mechanical vibrations of a micrometer-sized thin rectangular diamond plate, which is embedded in a specially designed square lattice fabricated on the diamond film. The vibrational energy level structure of the square lattice isolates and protects the compressional vibrations. Interactions between the qubit and the compressional vibrations will be investigated at the level of single quanta of the mechanical vibrations, with the goal of mediating and controlling interactions between two silicon-vacancy qubits through their coupling to the mechanical vibrations. In