Quantum optical rotatory dispersion, a technique that uses quantum methods to differentiate and measure molecules when light passes through chiral media, could offer a precise way to measure intricate molecular properties, even when low light or a low concentration of the molecule is used. An illustration of the quantum measurement of optical rotatory dispersion. Courtesy of Ralf Erlinger. Using multi-wavelength entangled photon pairs, researchers at Macquarie University and the University of Vienna measured the optical activity and optical rotatory dispersion exhibited by a solution of chiral molecules. The entangled photon states were used for quantum-enhanced measurements between different wavelengths and for measuring the dependence of optical activity on wavelength. The researchers’ scheme for probing wavelength dependence surpassed the information extracted per photon in a classical measurement; and could be used for more general differential measurements. “We sought out to understand how light couples to matter – which is at the core of many common instruments. Ultimately, we hope our findings can be used to find new ways to improve instruments like optical sensors and telescopes,” said associate professor Gabriel Molina-Terriza. The technique could be appropriate for analysis of samples that could be damaged by intense light, a potential concern for chiroptical studies. “We’ve found a way to analyze delicate samples by using less light,” said researcher Nora Tischler. “We hope to see this proof of concept built upon to eventually see efficiencies in the pharmaceutical sector, to more efficiently develop new medicines.” The researchers’ work paves the way for quantum-enhanced measurements of chirality, with potential applications in chemistry, biology, materials science and the pharmaceutical industry. The research was published in Science Advances (doi: 10.1126/sciadv.1601306).