Fig. 3. Distinguishable photon generation by spin control.

a Schematics for spin-controlled generation of distinguishable photons from a single h-V_Si centre. The sketch shows the realisation when the system is initially in the $m_{\mathrm{S}}=\pm \frac{1}{2}$ subspace. The first laser excitation results in a red photon (A₁ line). A subsequent RF pulse with variable duration transfers population (partially) from $m_{\mathrm{S}}=\pm \frac{1}{2}$ to $m_{\mathrm{S}}=\pm \frac{3}{2}$. The second excitation results in a blue photon (A₂ line), which makes the two interfering photons maximally distinguishable, and projects the system into the $m_{\mathrm{S}}=\pm \frac{3}{2}$ subspace. b Two-photon coincidence counts as a function of the delay time for a RF pulse duration of 19 ns (corresponding to a π/2-pulse). The coincidence peak at zero time delay reappears. Data are recorded at 0.1 ns timing resolution and averaged over three points to improve signal to noise. c Zoom-in of the HOM interference pattern revealing the fringe pattern with the expected modulation at 0.965 ± 0.006 GHz. Red dots are uncorrected data, and the blue line is the fit to the data (for details on the fit model, see Supplementary Note 7). d HOM contrast as a function of the RF pulse duration. Rabi-like oscillations are observed, demonstrating that coherent spin manipulation controls the degree of photon indistinguishability. Red dots are data and the blue line is the theoretical model considering independently measured Rabi oscillations (see Supplementary Note 4). Error bars represent one standard error.