Fig. presents the polariton population dynamics computed with a decoherence-corrected surface hopping approach. While the diabatic excited state population dynamics of |S 0 , 1⟩ (golden dotted line) and |S 1 , 0⟩ (purple dotted line) show a trend of smooth decays/increases, the upper polariton population P + (purple solid line) and lower polariton population P -(orange solid line) show oscillations which are mediated by of the polaritonic avoided crossing and polaritonic conical intersection. The consequence of these population transitions is that a large amount of population was transferred to the lower polariton whose curvature resists a conversion from the trans to the cis configuration, resulting in a quenching of the photoisomerization reaction rate relative to outside the cavity.