  Scalable quantum photonic networks require coherent excitation of quantum
emitters. However, many solid-state systems can undergo a transition to a dark
shelving state that inhibits the fluorescence. Here we demonstrate that a
controlled gating using a weak non-resonant laser, the resonant excitation can
be recovered and amplified for single germanium vacancies (GeVs). Employing the
gated resonance excitation, we achieve optically stable resonance fluorescence
of GeV centers. Our results are pivotal for the deployment of diamond color
centers as reliable building blocks for scalable solid state quantum networks.
