We theoretically study the temporal evolution of the mean number of photons in a strongly coupled cavity quantum dot system driven by a symmetric laser pulse using the Cluster Expansion method. The quantum dot is modeled as a two-level system that interacts with a single mode of the quantized electromagnetic field according to the Jaynes–Cummings model. We compare our results with those obtained through the Master Equation method and find that second-order Cluster Expansion is sufficient to reproduce the transmission spectrum without losing the fundamental physical processes and with a relatively low computational cost.