  We consider a potential landscape composed of a well region separated from a
"free" region by a barrier, such that one bound state and one quasi level exist
in the well. A particle initially in the ground state can be activated to the
quasi level by application of a micro wave field, and subsequently tunnel in
the free region. The wave function is then emitted by "bursts" after each Rabi
oscillation is completed, and the leakage current can be controlled by varying
the amplitude of the external field, the barrier height/width, and the
frequency mismatch.
