Theory for Entangled-Photons Stimulated Raman Scattering versus Nonlinear Absorption for Polyatomic Molecules

TL;DR

This paper develops a microscopic theory for entangled-photon stimulated Raman scattering (ESRS) in polyatomic molecules, showing how quantum correlations can enhance spectroscopic signals and comparing it to entangled two-photon absorption (ETPA).

Contribution

It introduces a theoretical framework for ESRS using entangled photons and identifies conditions where ESRS outperforms or matches ETPA in molecular spectroscopy.

Findings

Spectral-line intensity of ESRS is comparable to ETPA.

Time-energy correlation of photon pairs optimizes ESRS signals.

Vibrational coherence enhances ESRS over ETPA.

Abstract

Quantum entanglement offers an incredible resource for enhancing the sensing and spectroscopic probes. Here we develop a microscopic theory for the stimulated Raman scattering (SRS) using entangled photons. We demonstrate that the time-energy correlation of the photon pairs can optimize the signal for polyatomic molecules. Our results show that the spectral-line intensity of the entangled-photon SRS (ESRS) is of the same order of magnitude as the one for the entangled two-photon absorption (ETPA); the parameter window is thus identified to do so. Moreover, the vibrational coherence is found to play an important role for enhancing the ESRS against the ETPA intensity. Our work paves a firm road for extending the schemes of molecular spectroscopy with quantum light, based on the observation of the ETPA in experiments.