  Color centers in diamond are widely recognized as a promising solid state
platform for quantum cryptography and quantum information processing. For these
applications, single photon sources with a high intensity and reproducible
fabrication methods are required. Here, we report a novel color center in
diamond, composed of a germanium (Ge) and a vacancy (V) and named the GeV
center, which has a sharp and strong photoluminescence band with a zero-phonon
line at 602 nm at room temperature. We demonstrate this new color center works
as a single photon source. Both ion implantation and chemical vapor deposition
techniques enabled fabrication of GeV centers in diamond. A first-principles
calculation revealed the atomic crystal structure and energy levels of the GeV
center.
