for the motional narrowing. Here, the cavity loss is modeled by the Lindbladian (Eq. 10). It is straightforward to see from Eqs. 21 and 34 that under the resonance condition (ω c = ω 0 + λ), cavity loss contributes to the polariton linewidths by an amount of Γ c /2. Under the lossless limit of Γ c → 0, the polariton linewidths are dominated by exciton broadening, while under the lossy limit of Γ c ≫ Γ ex , the polariton linewidths are dominated by cavity broadening. Fig. presents the effect of cavity loss on polariton lineshapes. Here, we fix N = 4, the single molecule coupling strength g c = 68.1 meV, and the cavity frequency ω c = ω 0 + λ (resonance condition). The cavity loss rate varies from Γ c = 0 (lossless) to Γ c = 441.5 meV. One can see that as Γ c increases, the polariton linewidths gradually increase while the intensity decreases, and the total Rabi splitting decreases, consistent with Eq. 22. At a very high loss rate (Γ c > √ N g c ), one starts to see that two polariton peaks gradually merge into one, indicating that the strong-coupling condition (Eq. 23) is no longer fulfilled. Our numerical results are in line with the previous literature results .