Multiplexed scanning probe microscopy with spin qubits in diamond

While scanning probe microscopy with integrated quantum sensors continues to improve, multi-sensor probes remain underexplored despite their potential to advance imaging capabilities. Here, we present a multiplexed quantum sensing technique using scanning diamond probes containing multiple nitrogen-vacancy (NV) centers. A single optical channel is used to initialize and read out multiple qubits simultaneously. Phase- and frequency-dependent microwave spin manipulations demultiplex the readout signal, providing a route to access individual qubit measurements and their shared covariance. We demonstrate our technique by simultaneously imaging multiple magnetic field projections of a ferrimagnet and by recording the two-point magnetic field covariance across a current-carrying wire. With nanoscale spatial resolution, multiplexed scanning NV microscopy provides a unique platform for investigating a variety of correlated physical phenomena.