  Spin defects in silicon carbide (SiC) with mature wafer-scale fabrication and
micro/nano-processing technologies have recently drawn considerable attention.
Although room temperature single-spin manipulation of colour centres in SiC has
been demonstrated, the typically detected contrast is less than 2%, and the
photon count rate is also low. Here, we present the coherent manipulation of
single divacancy spins in 4H-SiC with a high readout contrast (-30%) and a high
photon count rate (150 kilo counts per second) under ambient conditions, which
are competitive with the nitrogen-vacancy (NV) centres in diamond. Coupling
between a single defect spin and a nearby nuclear spin is also observed. We
further provide a theoretical explanation for the high readout contrast by
analysing the defect levels and decay paths. Since the high readout contrast is
of utmost importance in many applications of quantum technologies, this work
might open a new territory for SiC-based quantum devices with many advanced
properties of the host material.
