The initial distribution {R, P} is then obtained by transforming { R, P} from the normal mode representation to the primitive coordinates using the unitary transformation that diagonalizes the Hessian matrix. All of the initial nuclear geometries for the quantum dynamics simulations are then sampled from the geometries centered at the optimized cis isomer (Fig. ), which is also used as the reference configuration to de-fine the global Cartesian system used in this work, see Sec. 4.2 for details. The detailed geometry for each trajectory, of course, fluctuates around the cis isomer, governed by the Wigner distribution. As the polariton dynamics proceed, the molecule will move and rotate in space. We do not remove any center of mass translation and rotation during the dynamics simulations.