New color centers in diamond for long distance quantum communication

Color centers in diamond are a promising platform for quantum communication, as they can serve as solid state quantum memories with efficient optical transitions. Much recent attention has focused on the negatively charged NV center in diamond, which has a spin triplet ground state electronic configuration that 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 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 (T 1 ) of around 40 ns at 5 K.