Fig. 4

Spatial resolution of quantum probe relaxation microscopy. a Schematic diagram of the diamond with patterned PMMA layers. b Bright-field image of the grating mask used to determine the image resolution. b Single τ _sp image of Cu²⁺ ions at 460 G (τ _sp = 124 µs, n = 12 × 10⁶). The light regions indicate areas of Cu²⁺. Scale bar in b, c is 5 µm. d Line cut through a section of the quantum probe relaxation image (yellow line). The Gaussian fit to each peak in the line scan shows linewidths of σ ₁ = 290 ± 30, σ ₂ = 330 ± 40 and σ ₃ = 540 ± 60 nm. The minimum linewidth is consistent with the diffraction limit of the microscope, ∼305 nm