Color centers in diamond are a promising platform for quantum information science, as they can serve as solid state quantum bits with efficient optical transitions. Much recent attention has focused on the negatively charged NV center in diamond, which can be measured and initialized optically, exhibits long spin coherence times at room temperature, and has narrow, spin-conserving optical transitions. However, the NV center exhibits a large static and dynamic inhomogeneous optical linewidth, and over 97% of its emission is in a broad, incoherent phonon side band, severely limiting scalability. Alternatively, the negatively charged SiV center exhibits excellent optical properties, with 70% of its emission in the zero phonon line and a narrow inhomogeneous linewidth. However, SiV- suffers from short electron spin coherence times, limited by an orbital relaxation rate (T1) of around 40 ns at 5 K. Informed by the limitations of NV- and SiV-, we have developed new methods to control the diamond Fermi level in order to stabilize the neutral charge state of SiV, thus accessing a new spin configuration. SiV0 exhibits a T1 approaching one minute at 4 K, and >90% of its emission is in its zero phonon line. These properties make it a particularly promising candidate for applications in long distance quantum communication.
