  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 thermalisation of isolated, interacting quantum
many-body systems. In this work we apply fidelity out-of-time-order correlators
to establish connections between thermalisation in Floquet system, the
exponential growth of FOTOCs as quantified by a non-zero quantum Lyapunov
exponent, and the underlying classical transition from regular to chaotic
dynamics in the dimer. Moreover, we demonstrate that a non-zero quantum
Lyapunov exponent can also be inferred from measures quantifying the
delocalisation of the Floquet modes of the system such as the Shannon entropy,
which approaches unity if the system thermalises to the periodic Gibbs ensemble
prediction.
