  A method for performing wave packet simulations in dipole fields is
presented. Starting from a Hamiltonian with non commuting terms, a gauge
transformation leads to a new Hamiltonian which allows to calculate explicitly
the evolution operator. In this new gauge, the dipole field is fully included
in the {\it vector} potential. The method of Goldberg, Schwartz and Schey based
on the Caley form of the evolution operator is then generalized, and the
resulting scheme is applied to describe a switching device based on Rabi
oscillations. The probability to tunnel in the free region exhibits a plateaux
structure as the wave function is emitted by ``bursts'' after each Rabi
oscillation has been completed.
