Quantum interference of entangled photon pairs
Parametric down-conversion (PDC) is a frequently-used technique to generate highly entangled photon pairs. We used this technique to examine the nature of quantum diffraction-interference caused by the entanglement. The figure shows the schematic view of the two-photon Mach-Zehnder interferometer we used in the experiment. The two-photon interference exhibited half the wavelength that observed in single photons, according to the "de Broglie wavelength" of the entangled photon pairs. See here.