State-dependent forces in cold quantum gases

This thesis develops a new way of modelling atoms that behave quantum mechanically on the inside, but classically on the outside. Doing so makes modelling the salient physics tractable. Prior to this technique, treating the outside of an atom classically failed to reproduce a bedrock experiment of quantum mechanics—the Stern–Gerlach experiment. I also report on the conception and flourishing of a control and analysis software suite for experiments in quantum science. This open-source project empowers experimenters to compose human-readable narratives upon their apparatus and has been adopted by a dozen groups worldwide.