Figure 1: The purification technique.

(a) Cartoon of the experiment: polarization pre- and postselection in a resonant transmission CQED experiment enables tuning of the photon statistics from antibunched to bunched. (b) Theoretical resonant transmission spectra for coherent light with mean photon number <<1, with and without the QD, comparing the conventional case (parallel polarizers) with the case of special polarization postselection along : close to one of the QD resonances, single-photon transmission is perfectly suppressed, despite the finite lifetime and cavity coupling of the QD transition. (c) Second-order correlation function for the special polarization angle case, comparing theory and experiment using two different sets of single photon counters (SPCs) with different timing jitter, 50 ps and 500 ps.