  Quantum sensors based on the nitrogen-vacancy (NV) centre in diamond are
rapidly advancing from scientific exploration towards the first generation of
commercial applications. While significant progress has been made in developing
suitable methods for the manipulation of the NV centre spin state, the
detection of the defect luminescence has so far limited the performance of
miniaturized sensor architectures. The recent development of photoelectric
detection of the NV centre's spin state offers a path to circumvent these
limitations, but has to-date required research-grade low current amplifiers to
detect the picoampere-scale currents obtained from these systems. Here we
report on the photoelectric detection of magnetic resonance (PDMR) with NV
ensembles using a complementary metal-oxide semiconductor (CMOS) device. The
integrated circuit delivers a digitized output of the diamond sensor with low
noise and 50 femtoampere resolution. This integration provides the last missing
component on the path to a compact, diamond-based quantum sensor. The device is
suited for continuous wave (CW) as well as pulsed operation. We demonstrate its
functionality with DC and AC magnetometry up to several megahertz, coherent
spin rotation and multi-axial decoupling sequences for quantum sensing.
