Quantum state control aided by single-molecule spectroscopy

Researchers at the Universität Innsbruck and the University of Warsaw have achieved non-destructive infrared absorption spectroscopy on a single molecular ion. The work overcomes a longstanding challenge in molecular physics: performing spectroscopy on individual molecules, typically hampered by low signal-to-noise ratios. By co-trapping a single CaOH+ molecular ion with an atomic ion, the team detected the absorption of a single photon via the momentum transfer from the absorbed photon onto the molecule and amplified the resulting recoil signal. This method, yielding a spectrum with single-photon sensitivity, offers a path toward measuring and preparing the quantum state of a wide range of molecular species. A single molecule’s vibrational response has been observed with…