(gaining thermal photon population). Then, a transition |ν L ⊗|1 → |ν L ⊗|0 will occur through the light-matter coupling term (Eq. E1), which will happen efficiently if and only if the energy of these two states are resonant, explaining both resonance effects of the rate profile and the resonance condition for observing Rabi splitting (Eq. E3). Then through the tunneling splitting ∆ , the transition |ν L ⊗ |0 → |ν R ⊗ |0 will occur, and eventually leading to a faster population grown of |ν R ⊗ |0 . In this work, we view the photonic DOF qc to play a similar role as "RPV mode", such that it enhances the activation process of |ν L → |ν L , which eventually leads to the enhanced product population P P (t). Because the cavity mode frequency ω c needs to match the |ν L → |ν L transition, the rate enhancement will be very sensitive to ω c , explaining the resonance effect of the VSC experiments. Note there is an interesting fact that because the cavity mode is purely harmonic (Eq. 2), the frequency ω c appeared in the Hamiltonian is identical to the frequency for the photonic state transition |0 → |1 . This is in contrast to the molecular system, where the quantum transition frequency ω 0 (Eq. 25) is not identical to the classical bottom-well frequency ω cl 0 (Eq. 26) when the potential is anharmonic.