Experimental study of a Back Action Evading device for continuos measurements on a macroscopic harmonic oscillator at the quantum limit level

Abstract.

The Back Action Evading technique is a particular kind of quantum non demolition measurement, first proposed by Caves et al. in 1980 [3]. We present an experimental study to implement the Back Action Evading measurement scheme in monitoring the amplitude of an harmonic oscillator excited by a classical force. Results showing the agreement of our theoretical model with the experimental behaviour of our apparatus in the classical regime are presented. We discuss also the optimization of the performance of our set-up, which should allow to monitor our oscillator in quantum regime even below the standard quantum limit level.