The invention of the laser provided a coherent source of light at high peak powers and was the necessary tool to open the world of nonlinear optics. One such example is two-photon absorption, which scales quadratically with the incident photon flux. A new paradigm began with the ability to generate more complicated states of light which possess novel correlations between photons. In this talk we begin with a review of the emerging field of “quantum nonlinear optics” and the controversy surrounding it. We then develop a model to analyze the interaction between quantum states of light and rubidium. We show that with strongly correlated pairs, two-photon absorption scales linearly with incident flux and can significantly enhance the rate of two-photon absorption compared to classical light in the low flux limit.