Speaker
Description
The fine-structure constant $\alpha$ can be determined with high precision through measurements of the ratio $h/m$ between the Planck constant and the atomic mass using atom interferometry. Our latest determination of $\alpha$ has achieved a relative uncertainty of $8.1\times 10^{-11}$, establishing recoil measurements as a cornerstone of precision metrology and tests of the Standard Model. However, discrepancies between the only independent determinations of $\alpha$ based on atom interferometry underscore the need for a refined understanding of related systematic effects.
Our recent work focuses on the study of systematic effects due to the laser beam profile. To extract the ratio $h/m$ from the recol velocity $\vec{v}_r = \hbar\vec{k}$, we must accurately determine the wave vector as perceived by the atoms in the vacuum chamber.
We demonstrate a novel method to map the spatial distribution of the wave vectors in situ using a Bose–Einstein condensate (BEC) as a localized probe. Due to its small spatial extent, the BEC samples the optical field with high resolution. By translating the condensate across the laser beam and performing recoil-sensitive atom interferometry at each position, we reconstruct a two-dimensional map of both the local intensity and the associated dispersion of $\vec{k}$. This approach, combined with numerical simulations, provides a powerful tool for evaluating one of the dominant systematic effects in recoil-based measurements of $h/m$ and $\alpha$.