Fig. 4

a Confocal fluorescence map of 500 × 500 nm (dwell time 2 ms and 1 nm pixel size) and b super-resolved image 300 × 300 nm of the white square in (dwell time 24 ms and 1 nm pixel size) b of two \({\text{NV}}^{ - }\) centres. The individual confocal spot is super-resolved into two separate dim fluorescence spots. c Cross section along the X-axis showing the separation of 72 nm between the two peaks corresponding to the locations of the centre-to-centre distance of the two NV centres. d Cross sections along the Y-axis with a measured FWHM resolution of 36 nm and 38 nm, corresponding to \({\text{NV}}^{ - }\) 1 and \({\text{NV}}^{ - }\) 2 in b, respectively