  We study a quantum system of coupled oscillators subject to a periodic
excitation of its parameters. Using Floquet-Lyapunov theory we derive the
linear integrals of motion of the system and relate their covariance matrix to
that for the canonical observables. The operator integrals allows us to
construct the intelligent (minimum uncertainty) states of the system and the
corresponding photon-added states. We found explicit expressions for the
wavefunction, Wigner function and covariance matrix of these states.
