Simplified Large-Momentum Transfer Atom Interferometry to Measure the Fine-Structure Constant

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Elementary particles interact, which means they impart forces on each other that can attract or repel. These forces determine how matter is built up from the fundamental particles, from atomic nuclei and atoms to molecules and solids. The fine-structure constant is a number that specifies the strength of electrical forces. Precision measurements of the fine-structure constant are important for many areas of physics, as they provide one of the most precise tests of the standard model of particle physics. These measurements can also be used to search for new particles. In 2018, with NSF support, the PI and coworkers published one of the most accurate measurements of the fine-structure constant to date. Subsequently, they have built a new apparatus with the goal of making an even more accurate measurement. In this new project they will complete this measurement by introducing three innovations that are intended to speed up progress and increase precision. As a broader benefit, this work will train undergraduate and graduate students in the technologies that enable quantum information science. This experiment functions by using photons to impart momentum kicks on atoms, and measuring the speed of the resulting atomic motion. From these measurements the fine-structure constant can be deduced. In this updated version of the experiment, the PI and coworkers will introduce three innovations. First, they will introduce a small temporal offset between two measurements that are usually done simultaneously. This will enable them to direct all of the laser power to just one of these measurements at a time, allowing them to use a larger laser-beam diameter. Second, they will make the paths taken by the atoms more symmetric, which will increase precision. Third, they will perform detailed modeling of the atoms’ paths to understand possible sources of measurement errors. 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.