  We perform a detailed analysis of the behavior of coherent and squeezed
states undergoing time evolution. We calculate time dependence of expectation
values of position and momentum in coherent and squeezed states (which can be
interpreted as quantum trajectories in coherent and squeezed states) and
examine how coherence and squeezing is affected during time development,
calculating time dependence of position and momentum uncertainty. We focus our
investigations on two quantum systems. First we consider quantum linear system
with Hamiltonian quadratic in $q$ and $p$ variables. As the second system we
consider the simplest quantum nonlinear system with Hamiltonian quartic in $q$
and $p$ variables. We calculate the explicit formulas for the time development
of expectation values and uncertainties of position and momentum in an initial
coherent state.
