2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/91282We employ a high quantum efficiency photon number counter to determine the photon number distribution of the output field from a parametric downconverter. The raw photocount data directly demonstrates that the source is nonclassical by forty standard deviations, and correcting for the quantum efficiency yields a direct observation of oscillations in the photon number distribution.Quantum Physicstext