Experimental Quantum Physics

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Non-classical interference of momentum entangled photons

In the process of spontaneous parametric down conversion (SPDC) a pair of photons can be generated out of a single photon. A direct consequence of energy and momentum conservation in SPDC are energy and momentum entanglement of the down converted photons.


Momentum entangled photons enable diffraction effects of half wavelength size as each of the two photons collects a phase – and these phases add up for a coherent superposition (entanglement) of their momenta.

The resolution of optical microscopes is limited by diffraction at the aperture of an objective. Using two momentum entangled photons the resolution can be improved by a factor of two.