GoKawiilPhysicists detect single molecular ion's vibrations using ultra-sensitive quantum sensor
Researchers built a two-ion crystal in a Paul trap combining a calcium ion with a single CaOH+ molecular ion, generated by leaking water vapor into the vacuum chamber until a molecule formed. They then used a non-classical 'cat state' of motion, created with a bichromatic laser on the calcium ion, to detect the tiny photon recoil from the molecule absorbing infrared light—effectively performing infrared absorption spectroscopy on one single polyatomic molecular ion.
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Measuring the vibrational spectrum of just one molecule at a time is a major step beyond bulk spectroscopy, which averages signals from trillions of molecules and can obscure fine quantum details. This technique could enable ultra-precise studies of molecular structure, chemical reactions, and even tests of fundamental physics using individually trapped and controlled molecular ions.
- Scientists trapped a single CaOH+ molecular ion alongside a calcium ion to enable precise spectroscopy.
- A quantum 'cat state' of ion motion was used to sense the recoil from a single photon absorption event.
- The method opens a path to studying molecular vibrations and chemistry at the single-particle quantum level.
Source: nature.com — Wu, 2026-08-26
Published there as: “Infrared absorption spectroscopy of a single polyatomic molecular ion”
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