  Neutrally charged divacancies in silicon carbide (SiC) are paramagnetic color
centers whose long coherence times and near-telecom operating wavelengths make
them promising for scalable quantum communication technologies compatible with
existing fiber optic networks. However, local strain inhomogeneity can randomly
perturb their optical transition frequencies, which degrades the
indistinguishability of photons emitted from separate defects, and hinders
their coupling to optical cavities. Here we show that electric fields can be
used to tune the optical transition frequencies of single neutral divacancy
defects in 4H-SiC over a range of several GHz via the DC Stark effect. The same
technique can also control the charge state of the defect on microsecond
timescales, which we use to stabilize unstable or non-neutral divacancies into
their neutral charge state. Using fluorescence-based charge state detection, we
show both 975 nm and 1130 nm excitation can prepare its neutral charge state
with near unity efficiency.
