Tunnelling through two barriers

Recent theoretical studies of the tunnelling through two opaque barriers claim that the transit time is independent of the barrier widths and of the separation distance between the barriers. Such a result is based on the use of the stationary phase method and the hypothesis of a single transmitted wave packet. In this Letter, we propose an alternative treatment based on a multiple peaks decomposition of the transmitted wave. We observe, that if multiple reflections are allowed for correctly (infinite peaks) the transit time between the barriers appears exactly as expected.