Photon bunching in parametric down-conversion with continuous-wave excitation

Abstract

Direct measurement of photon bunching (g (2) correlation function) in one output arm of a spontaneous-parametric-down-conversion source operated with a continuous pump laser in the single-photon regime is demonstrated. The result is in agreement with the statistics of a thermal field of the same coherence length and shows the feasibility of investigating photon statistics with compact continuous-wave-pumped sources. Implications for entanglement-based quantum cryptography are discussed. © 2009 The American Physical Society.