Chaos-assisted tunnelling in the absence of reflexion symmetry

It has been shown previously that a novel tunnelling behaviour, dubbed chao s-assisted tunnelling, can arise in bound, mixed phase space systems posses sing reflection symmetries. As with the usual, direct tunnelling problem of a double well, even a very weak symmetry breaking typically quenches the a bility of certain probability densities to tunnel resonantly back and forth . Experiments lacking exact reflexion symmetry will fail to exhibit tunnell ing. We show here how chaos-assisted tunnelling can be re-established exper imentally and distinguished from direct tunnelling through the variation of two external system parameters, and demonstrate the applicability of a gen eralized three-level model of the tunnelling process with the coupled quart ic oscillators.