Fig. 4: Data for a representative shallow implanted NV center (110 keV CN⁻).

a PLE spectra as measured (lower panel) and simulated (upper panel) similarly to Fig. 1d. Off-axial strain is estimated to be 12.6 GHz. The detuning is denoted from 637.20 nm. The 637 nm laser was tuned in resonance with the higher-energy transition at 19 GHz for all following measurements (red background). b Average fluorescence under optical pumping on the selected transition after explicit spin initialization according to Fig. 1c, as presented in Fig. 2a in the lower panel for the deep NV center. The NV⁻ center was initialized to |+1〉 with (70 ± 1)% probability. The background after 20 μs stems from finite excitation of the close-by |±1〉 transition. c Similar to Fig. 3a. Average fluorescence of the charge-state readout after charge initialization (without postselection), spin initialization in |+1〉 or |0〉 according to Fig. 1c, and spin-dependent ionization with varying ionization time. For d, an ionization time of 5 μs was used. d Similar to Fig. 3b. Distribution of the number of fluorescence photons for 5 ms of readout. The as-measured fidelity is (67.1 ± 0.9)%. e Simulation of the dipole transitions between optical ground and excited state for all three spin projection numbers for fixed strain-splitting of 20 GHz and varying magnetic field 20° off-axis. The transitions highlighted in yellow are the most pronounced spin |0〉 transitions. The coloring is a measure for the transition strength. There are several parameter ranges with spectrally well-isolated transitions.