Resolution and apodization in images generated by twin photons

We show that an image of an object is obtained when at least one of the photons of a parametric down-converted pair illuminates the object and the two photons are detected in coincidence after they have been transmitted by two lenses. The image is mathematically described by a quantum fourth-order correlation function that differs from the classical image description in two aspects. The quantum image is produced by a nonlocal effective lens whose aperture is described by a compressed convolution of the magnitude of lens transmission functions. The image is generated by the entangled state two-photon light source in which the effective wavelength is equal to the de Broglie wavelength λ/2, where λ is the wavelength associated to the individual photons. Images can be obtained with a resolution better than the obtained with coherent classical light sources. Better resolution and strong apodization effects are observed.