Fig. presents the results of our ab initio polariton quantum dynamics simulation, using the CASSCF ab initio calculation for all quantities, except for dipoles and their derivatives which are obtained from the machine learning model trained at the CASSCF level. Fig. presents the population dynamics of the polaritonic states, with the light-matter coupling strength g c = 0.005 a.u. (depicted in solid lines) and g c = 0.05 a.u. (depicted in open circles). When the light-matter coupling is relatively small (with coupling strength g c = 0.005 a.u.), the initial polariton population in |E 2 ⟩ decays very fast to the |E 1 ⟩ state in the first 60 fs of the dynamics. The population of the |E 0 ⟩ state begins to grow at ∼ 30 fs, and nearly all trajectories have hopped to the |E 0 ⟩ state at the end of the dynamics. Other highlying excited states, like |E 3 ⟩, |E 4 ⟩, |E 5 ⟩ are barely populated during the polariton dynamics process. Besides the polaritonic populations, we can also understand the population dynamics in the adiabatic-Fock states, as shown in Fig. . Since the light-matter coupling is weak when g c = 0.005 a.u. (depicted in solid lines), the |E 2 ⟩ state near the Franck-Condon region is mostly composed of the |e0⟩ state. Thus, the population of the |e0⟩ state is nearly one at the beginning of the dynamics. Then, the population transfers to the |g0⟩ state due to the electronic NAC between |e⟩ and |g⟩ states. During this process, we can see a small population of the |g1⟩ state, which is induced by the light-matter coupling dominated by the transition dipole between |e⟩ and |g⟩.