Interaction-driven breakdown of dynamical localization in a kicked quantum gas

Quantum interference can limit energy absorption in a continually kicked system through a single-particle ergodicity-breaking mechanism known as dynamical localization 1 , 2 . The effect of many-body interactions on dynamically localized states, although important to a fundamental understanding of quantum decoherence, has remained unexplored despite more than two decades of experimental studies 3 – 5 . Here we report the experimental realization of a kicked quantum rotor ensemble with tunable interactions using a Bose–Einstein condensate in a pulsed optical lattice. We observe a clear breakdown of dynamical localization due to interactions, but the resulting dynamics do not restore classical chaotic behaviour, instead displaying sublinear anomalous diffusion. Moreover, echo-type time-reversal experiments establish the role of interactions in destroying reversibility. These results quantitatively elucidate the dynamical transition to many-body quantum chaos and advance our understanding of quantum anomalous diffusion, with implications on the protection of quantum information in interacting driven systems.