Fig. 5: Spin cyclicity and single-shot readout.

a The spin is probed on the spin-preserving transition (red arrow in the level scheme in the inset), which is resonant with the cavity (blue curved lines), after initialization in the bright (orange) or dark (blue) state. An exponential fit to the average fluorescence (solid lines) allows determining the cyclicity ζ. Error bars: 1 SD. b After initialization, 71 pulses (red line in panel a and red circle in the inset) are applied on the spin-preserving line to read out the spin state. The probability distributions for the number of detected photons are clearly separated for the two initial spin states (orange and blue), thus allowing for readout with a fidelity of 86.9(8)% using a threshold photon number of one (red line). Inset: Single-shot readout fidelity depending on the number of readout pulses while choosing the optimal photon threshold.