We present the optimal estimation of an unknown squeezing transformation of the radiation field. The optimal estimation is unbiased and is obtained by properly considering the degeneracy of the squeezing operator. For coherent input states, the r.m.s. of the estimation scales as (2nˉ)−1 versus the average photon number nˉ, while it can be enhanced to (2nˉ)−1 by using displaced squeezed states.
@article{arxiv.quant-ph/0601103,
title = {Optimal estimation of squeezing},
author = {G. Chiribella and G. M. D'Ariano and M. F. Sacchi},
journal= {arXiv preprint arXiv:quant-ph/0601103},
year = {2007}
}