Surpassing the standard quantum limit for optical imaging using   non-classical multimode light
  Using continuous wave superposition of spatial modes, we demonstrate experimentally displacement measurement of a light beam below the standard quantum limit. Multimode squeezed light is obtained by mixing a vacuum squeezed beam and a coherent beam that are spatially orthogonal. Although the resultant beam is not squeezed, it is shown to have strong internal spatial correlations. We show that the position of such a light beam can be measured using a split detector with an increased precision compared to a classical beam. This method can be used to improve the sensitivity of small displacement measurements. 
N. Treps, U. Andersen, B. Buchler, P. K. Lam, A. Maitre, H.-A. Bachor   and C. Fabre