  The evolution of squeezed coherent states (CSs) of motion for trapped ions is
investigated by applying the time dependent variational principle (TDVP) for
the Schr\"{o}dinger equation. The method is applied in case of Paul and
combined traps, for which the classical Hamiltonian and equations of motion are
derived. Hence, CS provide a natural framework to: (a) engineer quantum
correlated states for trapped ions intended for ultraprecise measurements, (b)
explore the mechanisms responsible for decoherence, and (c) investigate the
quantum-classical transition.
