Classical and quantum photoemission from N-V centers in nanodiamonds

Single photons are currently used in quantum cryptography, quantum computation and quantum simulation. The most widespread single photon sources exploit either spontaneous parametric down-conversion of pump photons or emission from quantum dots. Here we develop a time coincidence confocal setup to study the emission from nitrogen-vacancy centers in nanodiamonds. By analizing the antibunching of photons in the second order correlation function we obtain an order of magnitude for the number of probed fluorescent centers. This is a first evidence of the transition from classical to quantum emission regime. The setup can be used to characterize home-made samples, such as ion implanted diamond films or nanodiamonds produced by pulsed laser ablation in liquid nitrogen.