Energy Superpositions in Entangled Two-Photon Absorption Spectroscopy

Quantum light-matter interactions are offering cutting-edge pathways to discover advanced functionalities at the atomic, molecular, and mesoscales. Motivated by these, in this work we investigate computationally the effect of energy quantum superpositions in the absorption of entangled photon pairs by molecular chromophores, where in addition to polarization uncertainty, the colors of the photon pairs are unknown as well. Based on time-dependenty density functional theory calculations, and a relatively simple modification of the theory of standard entangled two-photon absorption, we find that it is possible to considerably modify the absorption cross section of the molecular chromophores. Quantum constructive and destructive and interferences are computed, depending on the photonic states in the Bloch sphere. The destructive effects can be larger than the constructive ones. Our study could stimulate further theoretical/experimental work that examines energy superpositions.