  Atomic-scale impurity spins, also called color centers, in an otherwise
spin-free diamond host lattice have proven to be versatile tools for
applications in solid-state-based quantum technologies ranging from quantum
information processing (QIP) to quantum-enhanced sensing and metrology. Due to
its wide band gap, diamond can host hundreds of different color centers.
However, their suitability for QIP or sensing applications has only been tested
for a handful of these, with the nitrogen vacancy (NV) strongly dominating this
field of research. Due to its limited optical properties, the success of the NV
for QIP applications however strongly depends on the development of efficient
photonic interfaces. In the past years the negatively charged silicon vacancy
(SiV) center received significant attention due to its highly favourable
spectral properties such as narrow zero phonon line transitions and weak phonon
sidebands. We here review recent work investigating the SiV centre's orbital
and electron spin coherence properties as well as techniques to coherently
control its quantum state using microwave as well as optical fields and we
outline potential future experimental directions to improve the SiV's coherence
time scale and to develop it into a valuable tool for QIP applications.
