Enhanced and Selective Two-Photon Excitation of Molecular Vibronic States Using Entangled Photons

Abstract

We introduce molecular two-photon absorption and two-step excitation using quantum-mechanically entangled-photon pairs. The entangled photons possess the inherent simultaneity of photons originating from quantum correlation with energy anticorrelation, which is not shared by conventional laser light. This simultaneity enables entangled photons to achieve highly efficient two-photon absorption and two-step excitation under the condition of low light intensity. We show that ultrabroadband frequency-entangled photons can enhance the transition rates of two-photon absorption and two-step excitation more than 1000 times, compared to uncorrelated photons like laser light, and can also selectively excite a single vibrational mode in the molecular two-photon processes.