Super-sensitive polarization microscopy using NOON states of light
A quantum polarized light microscope using entangled NOON states with N = 2 and N = 3 is
shown to provide phase super-sensitivity beyond the standard quantum limit. We constructed such
a microscope and imaged birefringent objects at a very low light level of 50 photons per pixel, where
shot-noise seriously hampers classical imaging. The NOON light source is formed by combining a
coherent state with parametric down converted light. We were able to show improved phase images
with sensitivity close to the Heisenberg limit.