BSM-PM: Testing Fundamental Symmetries with A Novel Ytterbium Ion Clock

Any systematic study of Nature, from exploring sub-atomic structures to observing remote galaxies, finds that the texture of our universe is highly symmetric. In other words, there is a set of fundamental symmetry principles, which appear to hold universally on all length scales and energy scales. For instance, Einstein's theory of relativity rests on the concept that spacetime is symmetric: The laws of physics are supposed to be the same in all inertial reference frames and the speed of light is assumed to be the same in all directions. But how well can we experimentally test such symmetry assumptions? Given that physicists have by now gathered overwhelming evidence that our current understanding of Nature is incomplete, symmetry test experiments are crucial when looking for hints of "new physics" beyond the established models. In this project, the PI and his team want to further improve the precision of tests of fundamental symmetries by developing a particularly sensitive quantum detector for potential symmetry violations. They propose that a novel optical atomic clock based on ytterbium ions in a low-temperature environment may discover minute asymmetries or can deliver improved bounds on several potential symmetry violations. This project will also provide training for graduate and undergraduate students. These students will develop technical skills related to the research, as well as critical scientific judgment. More specifically, the team wants to investigate via high-precision laser spectroscopy a so far unexplored optical electric octupole (E3) transition in singly-charged ytterbium 173 confined in a cryogenic ion trap. Compared with measurements in room-temperature environments, black body radiation induced frequency shifts will be reduced to a negligible level. Similarly, frequency-shifting background gas collisions will be strongly suppressed. The improved spectroscopic precision combined with favorable atomic properties of the 173-Yb ion will make it possible to turn this optical atomic clock into a very sensitive antenna for potential effects of new physics beyond the Standard Model, e.g., the coupling of dark matter to quarks and gluons and violations of Lorentz symmetry in the strong force and electromagnetic sectors. 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.