University of Innsbruck researchers develop quantum method to measure single molecules

A research team led by experimental physicist Philipp Schindler at the University of Innsbruck has developed a new method for measuring individual molecules. Published in the journal Nature, the study demonstrates the ability to detect the absorption of a single photon to measure a single calcium hydroxide molecule.

Traditionally, molecular structures are understood by observing absorption spectra, which act as a molecular fingerprint. However, the signal from a single molecule is typically too weak to distinguish from background noise. To overcome this, the team utilized quantum logic spectroscopy, a technique derived from quantum information processing.

In this process, a difficult-to-access molecular ion is electromagnetically coupled with a highly controllable auxiliary atom within an ion trap. This allows the researchers to use the atom to amplify the tiny recoil momentum caused by a single infrared photon absorption, making the signal detectable.