Quantum optical rotatory dispersion

TL;DR

This paper demonstrates the first use of polarization-entangled photon pairs in quantum optical rotatory dispersion measurements, enhancing sensitivity and reducing sample damage in chiroptical studies.

Contribution

It introduces a quantum metrology approach using entangled photons to measure optical activity and dispersion, surpassing classical limits.

Findings

Quantum entangled photons improve measurement sensitivity.

Reduced sample damage compared to classical methods.

Potential applications in chemistry and biology.

Abstract

The phenomenon of molecular optical activity manifests itself as the rotation of the plane of linear polarization when light passes through chiral media. Measurements of optical activity and its wavelength dependence, optical rotatory dispersion, can reveal information about intricate properties of molecules, such as the 3D arrangement of atoms comprising a molecule. Given a limited probe power, quantum metrology offers the possibility to outperform classical measurements. This holds particular appeal when samples may be damaged by high powers, a potential concern for chiroptical studies. Here we show the first experiment in which multi-wavelength polarization-entangled photon pairs are used to measure the optical activity and optical rotatory dispersion exhibited by a solution of chiral molecules. Our work paves the way for quantum-enhanced measurements of chirality, with potential applications in chemistry, biology, materials science, and the pharmaceutical industry. The scheme we employ for probing the wavelength dependence allows to surpass the information extracted per photon in a classical measurement, and can also be used for more general differential measurements.