Femtosecond source of unbalanced polarization-entangled photons

We characterize a polarization-entangled photon source based on femtosecond pulsed parametric downconversion in a periodically poled χ(2) medium. Employing a Sagnac interferometer, we prepared different quantum states aiming at future investigations in quantum information and on the foundations of quantum mechanics. In this work we demonstrate the controlled generation of unbalanced entangled states, rather than the usual maximally entangled ones, by tuning the polarization of the system’s pumping field.