Macroscopic matter wave quantum tunnelling

Quantum tunnelling is a phenomenon of non-equilibrium quantum dynamics and its detailed process is largely unexplored. We report the experimental observation of macroscopic quantum tunnelling of Bose-Einstein condensate in a hybrid trap. By exerting a non-adiabatic kick to excite a collective rotation mode of the trapped condensate, a periodic pulse train, which remains as condensate, is then out-coupled by quantum tunnelling. This non-equilibrium dynamics is analogue to tunnelling ionization. The imaged tunnelling process shows the splitting of matter wave packet by the potential barrier. The controversial "tunnelling time" question is found inadequate, from the point of view of wave propagation. The realized matter wave pulse train can also be a passive pulsed atom laser for atom interferometer applications. Quantum tunnelling as a non-equilibrium process is a problem of quantum physics that has been investigated in several microscopic systems. Motivated by attosecond ionization experiments and the puzzle of tunnelling time, the authors report experimental results on the quantum tunnelling of a Bose-Einstein Condensate out of an optical dipole trap.