Instantaneous measurements of quadrature moments of cavity fields with strongly driven atoms

We propose a scheme for measuring the mean value of quadrature moments of one- and two-mode cavity fields by considering the resonant atom-cavity interaction in the presence of strong classical driving fields. With the aid of strong classical fields, it is easy to realize the quadrature operators for cavity fields, which are correlated to the internal state of the two-level atom. It is shown that the mean value of quadrature moments of cavity fields is determined by the time derivative of the population of the internal state at the initial interaction time. The scheme can be directly used to test quantum entanglement of two-mode cavity fields