Fig. 1. Schemes to measure g(2)(τ) based on prototype measurements with (a) a tunable electronic delay and (b) a start-stop process with a TAC-MCA system. (c) and (d) show the differences between g(2)(τ) and C(τ) for the Poisson distribution (g(2)(τ)=1; C(τ)=e−aτ) and antibunched photons (g(2)(τ)=1−e−bτ; C(τ)=e−aτ−e−bτ).

Fig. 2. Schematics of the experimental configuration with a home-built confocal microscope setup and HBT measurement. The diamond sample with a NV center on the piezo-stage (PZT) was excited by a continuous laser (λ=532  nm) through an objective with N.A.=0.9. The dichroic mirror (DM) was used to reflect the pump beam and transmit the fluorescent photons. The long pass (LP) filter further blocked the pump photons. The BS separated the photons into two SPCMs, followed by two g(2)(τ) measurement schemes.

Fig. 3. Results from the prototype measurement with tunable electronic delay (large red dots, obtained by averaging the results of several repeated measurements) and the TAC-MCA system (small black dots). (a) The inset shows the measurement results with τ<1  μs, which indicates negligible differences. (b) shows the measurement results with τ up to 20 μs and nstop=60  k/s. Obvious differences can be observed.

Fig. 4. Measurement results from the prototype measurement with tunable electronic delay (large dots) and TAC-MCA system (small dots) with different counting rates of the stop channel (nstop). The results from the prototype measurement shows little variation, while the data from TAC-MCA system have different results. The indices 1, 2, 3, 4, 5, 6 corresponded to nstop=10,20,30,40,50,and 60  k/s.

Fig. 5. (a) shows the fitting result of C(τ) with a single exponential decay function. nstop=60  k/s; (b) is the fitting of a with a linear function according to the counting rates of the stop channel (nstop); and (c) is the correction results for different nstop. The indices are the same with Fig. 4.