Current noise in a irradiated point contact

We propose a new approach to calculate current and current correlations in a ballistic quantum point contact interacting with a classical field. The approach is based on the concept of scattering states for a time dependent Hamiltonian neglecting electron-electron interaction. Using this approach we calculated the spectra of the current noise in a biased point contact irradiated by a weak random field. For typical radiation frequencies \nu less than the temperature T and the bias voltage V we find a narrow peak of width \nu on top of a broad background of width \max (T,eV).