Pulsed Macroscopic Quantum Tunneling of Falling Bose Condensates

We investigate macroscopic quantum tunneling of a Bose condensate and how it is affected by the interatomic interaction. We study the dynamics of a condensate falling under gravity and scattering on a Gaussian potential barrier that models a mirror formed by a far-detuned sheet of light. We observe bouncing, interference and quantum tunneling of the condensate. We find that the tunneling rate is very sensitive to the interatomic interaction and to the shape of the condensate. Under many conditions the tunneling rate is strongly enhanced by the interaction as achieved, for instance, by increasing the number of condensed particles. In a quasi 1D situation the tunneling pulse displays two peaks. The quantum tunneling can be quasi-periodic and in this way one could generate coherent Bose condensed atomic pulses. PACS numbers: 03.75.Fi, 32.80.Pj, 42.50.Vk