Exact solution of the two-mode quantum Rabi model

Qiong-Tao Xie

Figure 2. Energy spectrum of the two-mode QRM as a function of g/ω for two different values of (a) Δ/ω = 2 and (b) Δ/ω = 3 with ω = 1. In (a), the circles denote the exact energies ${E}_{1,3/2}^{\mathrm{II}}$ at the resonant condition of ${\rm{\Delta }}/\omega =2\kappa -1=2$, and in (b), the circles denote the exact energies ${E}_{1,2}^{\mathrm{II}}$ at the resonant condition of ${\rm{\Delta }}/\omega =2\kappa -1=3$.