Manipulating Two-Photon Absorption of Molecules through Efficient Optimization of Entangled Light

TL;DR

This paper introduces a Bayesian optimization protocol to enhance and control two-photon absorption in molecules using entangled photons, enabling selective excitation beyond classical light capabilities.

Contribution

The authors develop a novel Bayesian optimization method for manipulating two-photon absorption with entangled light, demonstrating significant enhancement and selectivity in molecular excitation.

Findings

Entangled two-photon absorption probability increased by up to 20 times.

Classical light cannot be optimized for similar excitation.

Entangled light can excite states inaccessible to classical light.

Abstract

We report how the unique temporal and spectral features of pulsed entangled photons from a parametric downconversion source can be utilized for manipulating electronic excitations through the optimization of their spectral phase. A new comprehensive optimization protocol based on Bayesian optimization has been developed in this work to selectively excite electronic states accessible by two-photon absorption. Using our optimization method, the entangled two-photon absorption probability for a thiophene dendrimer can be enhanced by up to a factor of 20 while classical light turns out to be nonoptimizable. Moreover, the optimization involving photon entanglement enables selective excitation that would not be possible otherwise. In addition to optimization, we have explored entangled two-photon absorption in the small entanglement time limit showing that entangled light can excite molecular electronic states that are vanishingly small for classical light. We demonstrate these opportunities with an application to a thiophene dendrimer.