2STICKY · Two-body loss and sticky collisions in ultracold molecule-atom systems

Ultracold bialkali molecules are promising platforms for quantum simulation, computation, and precision tests of fundamental physics. However, their practical application is severely limited by unexpected two-body losses, attributed to ""sticky collisions"" where molecules form long-lived complexes prone to photoexcitation by trapping light. The standard statistical theory for describing these collisions provides an incomplete picture: while it explains loss rates in some systems, complex lifetimes measured in molecule-atom collisions exceed predictions by several orders of magnitude. Furthermore, a major class of experiments designed to mitigate these losses often yields inconclusive ""null results"" when no loss suppression is observed, exposing a critical lack of robust observables and hindering further progress.This project, ""Two-body loss and sticky collisions in ultracold molecule-atom systems"" (2STICKY), will resolve this impasse through a comprehensive theoretical approach. First, it will perform the first rigorous benchmark of the statistical model against exact quantum scattering calculations. It will then be extended by developing the first ab initio treatment of symmetry-breaking interactions, such as hyperfine couplings, to provide a realistic framework capable of explaining experimental discrepancies. Finally, the project will establish a new theoretical toolkit to extract physical observables from experiments by exploring signatures of quantum chaos, fundamentally changing how data is interpreted.This work will equip the fellow with a unique interdisciplinary skill set at the intersection of quantum chemistry and ultracold physics, preparing him to establish his own independent research program in the European Research Area.""