Abstract:Â For the past two decades harmonically trapped ultracold atomic gases have been used with great success to study fundamental many-body physics in flexible experimental settings. However, the resulting gas density inhomogeneity in those traps has made it challenging to study paradigmatic uniform-system physics (such as critical behavior near phase transitions) or complex quantum dynamics. The realization of homogeneous quantum gases trapped in optical boxes has been a milestone in quantum simulation [1]. These textbook systems have proved to be a powerful playground by simplifying the interpretation of experimental measurements, by making more direct connections to theories of the many-body problem that generally rely on the translational symmetry of the system, and by altogether enabling previously inaccessible experiments. I will give an overview of recent studies on the quantum many-body physics of fermions in a box of light. These studies span the few-body recombination physics of multi-component fermions [2,3], the observation of the fermionic quantum Joule-Thomson effect [4], the strong-drive spectroscopy of Fermi-polaron quasiparticles [5], and the observation of the Lindhard response
[6]. These studies have led to some surprising results (including an open puzzle on three- component fermions [3]), highlighting how spatial homogeneity not only provide quantitative
advantages, but can also unveil truly unexpected outcomes. [1] N. Navon, R.P. Smith, Z. Hadzibabic, Nature Phys. 17, 1334 (2021) [2] Y. Ji et al., Phys. Lev. Lett 129, 203402 (2022) [3] G.L. Schumacher et al., arXiv:2301.02237, Nature Comm. in press (2025) [4] Y. Ji et al., Phys. Lev. Lett 132, 153402 (2024) [5] F.J. Vivanco et al., arXiv:2308.05746, Nature Phys. in press (2025) [6] S. Huang et al., arXiv:2407.13769, Phys. Rev. X in press (2025)