V. A. Buts

It is shown that the regimes with dynamic chaos are quite characteristic for quantum systems. Especially it is necessary to emphasize that such regimes appear characteristic not only in semiclassical approach but also for meanings of parameters which do not allow one to use semiclassical approximation. Thus, it is shown that in quantum systems (linear systems) there can be regimes with true dynamic chaos. As an example the three-level system which is under action of external periodic perturbation is considered. Such model is most typical for quantum systems. It is known that to such models the large number of real quantum systems are reduced, in particular, atoms and nucleuses which are under influence of external laser radiation. The conditions of dynamic chaos arising in such three-level system are analytically found. The numerical methods show the good qualitative consent with the received analytical results. The occurrence of dynamic chaos has allowed using the methods of statistical physics. Thus it was shown, that in energy space, at performance of conditions of dynamic chaos, diffusion process arises. In these conditions, the quantum system can pass to higher power levels with the much greater efficiency than at multiphoton processes.