  We show that the conditional displacement operator $\hat{U}_{CD}=\exp
[\hat{b}^{\dagger}\hat{b}(\beta \hat{a}^{\dagger}-\beta ^{\ast}\hat{a})]$
acting upon an arbitrary state of traveling waves can be well approximated by
the action of a Kerr medium placed between two beam splitters whose respective
second ports are fed by highly excited coherent states. Applications to the
generation of nonclassical states and measurement of Wigner function of
arbitrary states are also considered.

Quantum Physics