  In this thesis concrete quantum systems are investigated in the framework of
the environment induced decoherence. The focus is on the dynamics of highly
nonclassical quantum states, the Wigner function of which are negative over
some regions of their domains. One of the chosen physical systems is a diatomic
molecule, where the potential energy of the nuclei is an anharmonic function of
their distance. A system of two-level atoms, which can be important from the
viewpoint of quantum information technology, is also investigated. A method is
described that is valid in both systems and can determine the characteristic
time of the decoherence in a dynamical way. The direction of the decoherence
and its relation to energy dissipation is also studied. Finally, a scheme is
proposed that can prepare decoherence-free states using the experimental
techniques presently available.
