Stochastic simulations: continuous approximation of quantum noise

The stochastic simulations of quantum evolution are introduced, alternative ly, to the Ito-stochastic simulations, for the normal, symmetrical and anti normal ordering in the double-dimensional phase space. The nonclassical eff ects in the linearized parametric amplifier can be very well simulated in c ontrast to the collapses-revivals effect in a nonlinear version, which is s timulated by the discreteness of light. The reason is that the stochastic s imulations use the continuous variables, whereas the quantum noise in nonli near systems cannot generally be treated continuously.