Perturbative nonlinear feedback forces for optical levitation experiments

Feedback control can be used to generate well-determined nonlinear effective potentials in an optical trap, a goal whose applications may range from nonequilibrium thermodynamics to the generation of non-Gaussian states of mechanical motion. Here, we investigate the action of an effective feedback-generated quartic potential on a levitated nanoparticle within the perturbation regime. The effects of feedback delay are discussed and predictions from the perturbation theory of a Brownian particle subjected to a quartic anharmonicity are experimentally verified.