  We discuss quantum dynamics in multi-dimensional non-linear systems. It is
well-known that wave functions are localized in a kicked rotor model. However,
coupling with other degrees of freedom breaks the localization. In order to
clarify the difference, we describe the quantum dynamics by deterministic rigid
trajectories, which are accompanied with the de Broglie-Bohm interpretation of
quantum mechanics, instead of wave functions. A bundle of quantum trajectories
are repulsive through quantum potential and flow never to go across each other.
We show that, according to the degrees of freedom, this same property appears
differently.
