  Terahertz technologies are important for a number of emerging applications,
such as for next generation communications. We predict that transition metal
substitutional defects in two-dimensional transition metal dichalcogenides
(TMDs) can serve as quantum defects for terahertz technologies. Central to this
prediction is the finding that the zero field splittings between spin sublevels
in such defects are typically in the sub-terahertz to terahertz range due to
the large spin-orbit coupling in these systems. As a proof of concept, we
consider different transition metal impurities from across the periodic table,
in prototypical TMDs, MoS2 and WSe2. Using first principles calculations, we
demonstrate that selected spin triplet defects can potentially serve as qubits
operating in the terahertz regime. We also propose defects that can potentially
be quantum sources of terahertz radiation. Our research broadens the scope of
advancements in quantum information science and lays a foundation for their
integration with THz technologies.
