  Here we consider the time evolution of a one-dimensional quantum system with
a double barrier given by a couple of two repulsive Dirac's deltas. In such a
"pedagogical" model we give, by means of the theory of quantum resonances, the
explicit expression of the dominant terms of $<\psi, e^{-it H} \phi >$, where
$H$ is the double-barrier Hamiltonian operator and where $\psi$ and $\phi$ are
two test functions.
