  Strong light-matter interactions are critical for quantum technologies based
on light, such as memories or nonlinear interactions. Solid state materials
will be particularly important for such applications, because of the relative
ease of fabrication of components. Silicon vacancy centers (SiV) in diamond
feature especially narrow inhomogeneous spectral lines, which are rare in solid
materials. Here, we demonstrate resonant coherent manipulation, stimulated
Raman adiabatic passage, and strong light-matter interaction via four-wave
mixing of a weak signal field in an ensemble of SiV centers.
