Solution of the two-mode quantum Rabi model using extended squeezed states

Understand

The two-mode quantum Rabi model with bilinear coupling is studied using extended squeezed states.

• We derive $G$-functions for each Bargmann index $q$% .
• They share a common structure with the $G$-function of the one-photon and two-photon quantum Rabi models.
• The regular spectrum is given by zeros of the $G$-function while the conditions for the presence of doubly degenerate (exceptional) eigenvalues are obtained in closed form through the lifting property.