Bunching and antibunching from single NV color centers in diamond
  We investigate correlations between fluorescence photons emitted by single N-V centers in diamond with respect to the optical excitation power. The autocorrelation function shows clear photon antibunching at short times, proving the uniqueness of the emitting center. We also report on a photon bunching effect, which involves a trapping level. An analysis using rate-equations for the populations of the N-V center levels shows the intensity dependence of the rate equation coefficients. 
A. Beveratos, R. Brouri, J.-P. Poizat, P. Grangier