Achieving quantum-limited optical resolution
  We establish a simple method to assess the quantum Fisher information required for resolving two incoherent point sources with an imaging system. The resulting Cram\'er-Rao bound shows that the standard Rayleigh limit can be surpassed by suitable coherent measurements. We explicitly find these optimal strategies and present a realization for Gaussian and slit apertures. This involves a projection onto the optimal bases that is accomplished with digital holographic techniques and is compared with a CCD position measurement. Our experimental results unequivocally confirm unprecedented sub-Rayleigh precision. 
Martin Paur, Bohumil Stoklasa, Zdenek Hradil, Luis L. Sanchez-Soto and   Jaroslav Rehacek
quant-ph