Abstract

We show that a measurement setup where N systems interact with a N +1st system allows one to achieve Heisenberg limited sensitivity, where the smallest resolvable change in an observable x scales as d x 1=N, without using or ever creating any entanglement. The method is robust under local decoherence, in the sense that decoherence changes only the prefactor but not the scaling with N. We propose a possible application in high precision measurements of the length of an optical cavity.

© 2012 Optical Society of America