Two-Photon Optics: Imaging below the diffraction limit

The properties of imaging systems can be described by the point-spread function, which is determined by diffraction. A shorter wavelength results in a smaller diffraction pattern and therefore allows (in principle) a better resolution. It has been shown that entangled n-photon states have diffraction properties of the wavelength divided by n if a n-photon detection is performed. Here we use this feature to enhance the resolution of an imaging system.