  By exploiting the quantised nature of light, we demonstrate a sub-shot-noise
scanning optical transmittance microscope. Our microscope demonstrates, with
micron scale resolution, a factor of improvement in precision of 1.76(9) in
transmittance estimation gained per probe photon relative to an optimal
classical version at the same optical power. This would allow us to observe
photosensitive samples with nearly twice the precision,without sacrificing
image resolution or increasing optical power to improve signal-to-noise ratio.
Our setup uses correlated twin-beams produced by parametric down-conversion,
and a hybrid detection scheme comprising photon-counting-based feed-forward and
a highly efficient CCD camera.
