Cold molecules as precision sensors for the weak interaction

The goal of physics is to find the fundamental laws that govern our universe. In recent decades, progress in this direction has often come from particle accelerators and other large- scale research facilities. However, a new avenue of exploration is emerging through high- precision experiments that can be performed in smaller setups. This project focuses on using well-controlled molecules to realize such compact precision sensors to provide a new window into fundamental physics. To achieve the extraordinary precision required, the project will use tools to control quantum systems. While these tools have been widely applied to simple quantum systems such as atoms or photons, their application to more complex molecules is a topic of ongoing research worldwide. Specifically, the project aims to prepare cold molecular ensembles by laser cooling. The reduced temperature of the molecules will allow them to be manipulated and probed for extended periods of time, which is a key ingredient to increase the precision of the planned measurements. The second key ingredient are the molecules themselves and the use of their quantum mechanical structure for precision measurements. To achieve this, the project will focus on barium monofluoride (BaF) molecules. The structure of these molecules makes them inherently highly sensitive to the symmetries that underlie many fundamental laws of physics. There are four fundamental forces of nature - gravity, electromagnetism, the weak force, and the strong force. One of the four, the weak force, violates what is known as parity symmetry. This means that the fundamental laws describing this force change when viewed through a mirror. BaF molecules can help amplify the tiny effects associated with this broken symmetry, making them accessible for measurement. The detailed characterization of these effects in this project will provide insights complementary to those obtained at large research facilities, and may thus help to gain unprecedented insights into the inner workings of our universe.