where the original coupling strength λ has been broadened by the Lorentzian function, with ∆ω = ω k+1 -ω k as the discrete mode frequency separation, ω c as the central mode frequency, and ω k as the frequency of the k th mode. In this work, 193 36,000 cavity modes were used to mediate the cavity loss effects for an effective single-mode cavity. Recall that λ is a generalization of the commonly used Jaynes-Cummings coupling strength g c and can be related as g c = ωc 2 λµ eg in Eq. 3. This approach to cavity loss is, in principle, equivalent to adding a photonic bath to the cavity mode qc (see Eq. 185 in Sec. 4.7). The loss rate κ can be directly measured from experiments by the width of the absorption peak assuming that the spectral width is dominated by the photonic loss, which is a good approximation for most realistic experimental configurations. In Fig. , the absorption spectra (see details in Sec. 3.3.2) was computed 99 using the effective polaritonic dipole by mixing the electronic dipoles according to expansion coefficients of the adiabatic electronic and Fock basis states