  As one of the famous effects in quantum Rabi model (QRM), Rabi oscillation
may lead to the occurrence of quantum dynamics behaviors without classical
dynamic counterparts, such as quantum collapse and revival effects. In this
paper, we focus on studying whether the entanglement entropy and Husimi Q
function, as diagnostic tools for quantum chaos in quantum systems, are
invalidated by quantum collapse and revival. It is shown that the saturation
values of entanglement entropy for initial states located in the chaotic sea of
QRM are higher than that in the regular regions. When the system reaches
dynamic equilibrium, the Husimi Q function which initial states located in the
chaotic sea are more dispersed than that in the regular regions. Moreover, we
observe a good correspondence between the the time-average entanglement entropy
and classical phase space structures. Our results imply that entanglement
entropy and Husimi Q function maintain the function for diagnosing chaos in the
QRM and the corresponding principle does not be invalidated by quantum collapse
and revival effects in this system.
