Towards Molecular Control and Rational Design of Molecules with Enhanced Entangled Two-Photon Absorption.

Abstract

We utilize entangled photons to carry out nonlinear optical spectroscopy in organic molecules with an extremely small number of photons. While much research has been devoted to utilizing quantum mechanics and quantum entanglement in areas of quantum computing, quantum information science and quantum cryptography, the goal of this research is to exploit quantum entanglement in the area of spectroscopy. One unique feature that is observed when using such non-classical fields to carry out multi-photon absorption is the selectivity of the entangled photon absorption process. It is found that while some molecules may not have strong classical nonlinear optical properties, due to their excitation pathways, these same excitation pathways may enhance the entangled photon processes. It is found that the opposite is also true. It is proposed that molecules that absorb via a virtual state pathway absorb entangled photons and those that absorb via a change in permanent dipole do not. A modified equation for calculating the entangled two-photon absorption cross-section is derived. Using this modified equation we calculate and compare the entangled two-photon absorption cross-section of both homo and hetero-nuclear diatomic molecules. We hope this comparison expands upon previous theoretical work in the area of entangled two-photon absorption and provides more insight into the absorption mechanisms of non-classical fields.