A 2-STEP OPTIMIZED MEASUREMENT FOR THE PHASE-SHIFT

A two-step detection strategy is suggested for the precise measurement of the optical phase shift. In the first step an unsharp, but unbiase d, joint measurement of the phase and photon number is performed by he terodyning the signal field. Information coming from this step is then used for appropriate squeezing of the probe made to obtain a sharp ph ase distribution. Application to squeezed states leads to a phase sens itivity scaling as Delta phi similar or equal to N-1 relative to the t otal number of photons impinged onto the apparatus. Numerical simulati ons of the whole detection strategy are also presented. (C) 1998 Publi shed by Elsevier Science B.V.