  Neutral silicon vacancy (SiV0) centers in diamond are promising candidates
for quantum networks because of their excellent optical properties and long
spin coherence times. However, spin-dependent fluorescence in such defects has
been elusive due to poor understanding of the excited state fine structure and
limited off-resonant spin polarization. Here we report the realization of
optically detected magnetic resonance and coherent control of SiV0 centers at
cryogenic temperatures, enabled by efficient optical spin polarization via
previously unreported higher-lying excited states. We assign these states as
bound exciton states using group theory and density functional theory. These
bound exciton states enable new control schemes for SiV0 as well as other
emerging defect systems.
