Imaging beyond the Rayleigh bound

We demonstrate resolution below an imaging system's Rayleigh bound using an arbitrary object-covering scan with focused illumination and N-photon detection, as proposed by Giovannetti et al. [1]. We observed a resolution enhancement by a factor of ∼(N-N̄ max) 1/2 with N̄ max being the maximum average detected photon number in the image. Our results are in agreement with theory, which predicts this improvement factor up to the limit set by the size of the illuminator beam