BSM-PM: RUI: molecular vibrations as quantum sensors of new physics

The National Science Foundation Division of Physics awarded Amherst College, Trustees Of $625,000 on August 1, 2026, under the Mathematical and Physical Sciences program (CFDA 47.049) to investigate laser-driven vibrational transitions in molecular ions as a platform for optical molecular clocks sensitive to fundamental physical constants.

The project develops molecular vibrations in diatomic oxygen molecular cations as quantum sensors, focusing on the ground-to-excited vibrational state transition. This transition exhibits a narrow natural linewidth, high sensitivity to changes in fundamental physical constants such as proton-to-electron mass ratios, and long-term potential as an optical molecular clock. The nonpolar nature of the molecule suppresses systematic shifts from electric field effects, including AC Stark shifts and blackbody radiation. The work advances quantum information science through development of molecular vibration as a quantum sensor of time and improvements in techniques for trapping and controlling quantum states of individual atoms and molecules. The research seeks to detect variations predicted by models of quantum gravity or dark matter.

Work is performed in Amherst, Massachusetts, with a period of performance from August 1, 2026, through July 31, 2029. Undergraduate students participate as key contributors to all aspects of research, and the project supports the career advancement of a postdoctoral scholar, developing experimental and technical skills applicable across scientific careers.

Abstract

Atoms and molecules follow the laws of quantum mechanics. Their energies are ?quantized? Meaning they can only exist in certain states. Some of these states are particularly well-suited to use in timekeeping, quantum information, or tests of physical laws. This award focuses on molecular vibrations ? The stretching and compressing of a chemical bond between atoms. The project will use the extremely stable oscillation of these vibrations as the pendulum of a molecular clock. This new type of clock will be sensitive to tiny changes in the basic physical parameters of nature, such as the mass ratio of protons to electrons. Such changes are predicted by models of quantum gravity or dark matter. This work will promote the progress of science in searching for such new physics. IT will advance the priority research area of quantum information science by developing molecular vibration as a quantum sensor of time as well as improving techniques for trapping individual atoms and molecules and controlling their quantum states. This research takes place at a primarily undergraduate institution, and undergraduate students will be key contributors to all aspects of the work. The project will advance the career of a postdoctoral scholar. In addition to training the next generation of scientists, this work will develop experimental and technical skills that are valuable in many careers. This award enables investigation of laser-driven vibrational transitions in molecular ions. The particular transition here ? From the ground vibrational state to a vibrationally excited state in the diatomic oxygen molecular cation ? Has a narrow natural linewidth, high sensitivity to changing fundamental constants, and long-term prospects as an optical molecular clock. The nonpolar nature of the molecule suppresses systematic shifts related to electric fields, such as AC stark shifts and blackbody radiation. Molecular vibrations hold great promise for next-generation searches for drifts or oscillations in the proton-to-electron mass ratio. This project builds on the PI?s experience with trapped charged particles as well as existing infrastructure for producing, trapping, and cooling quantum-state-selected molecular ions. These ions will be loaded into a trap and sympathetically cooled with CO-trapped atomic ions. The trapping enables long probe times, which will be needed to precisely determine the transition frequency and to demonstrate a proof-of-principle search for variation in the proton-to-electron mass ratio. Such a search is a probe of additional dimensions, new scalar fields, and ultralight dark matter. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the foundation's intellectual merit and broader impacts review criteria.- subawards are not planned for this award.