Thermalization in a Bose-Hubbard dimer with modulated tunneling

The periodically modulated Bose-Hubbard dimer model offers an experimentally realizable and highly tunable platform for observing the scrambling of quantum information and the apparent thermalization of isolated, interacting quantum many-body systems. In this work we apply fidelity out-of-time correlators (FOTOCs) to establish connections between the thermalization in the Floquet system, the exponential growth of FOTOCs as quantified by a nonzero quantum Lyapunov exponent, and the underlying classical transition from regular to chaotic dynamics in the dimer. Moreover, we demonstrate that a nonzero quantum Lyapunov exponent can also be inferred from measures quantifying the delocalization of the Floquet modes of the system such as the Shannon entropy, which approaches unity if the system thermalizes to the periodic Gibbs ensemble prediction.