  For 1D quantum harmonic oscillator perturbed by a time quasi-periodic
quadratic form of $(x,-{\rm i}\partial_x)$, we show its almost reducibility.
The growth of Sobolev norms of solution is described based on the scheme of
almost reducibility. In particular, an $o(t^s)-$upper bound is shown for the
$\CH^s-$norm if the equation is non-reducible. Moreover, by Anosov-Katok
construction, we also show the optimality of this upper bound, i.e., the
existence of quasi-periodic quadratic perturbation for which the growth of
${\mathcal H}^s-$norm of the solution is $o(t^s)$ as $t\to\infty$ but
arbitrarily ``close" to $t^s$ in an oscillatory way.

Analysis of PDEs;Dynamical Systems