Precision measurement of a trapping potential for an ultracold gas

•Parametric excitation of ultracold atoms in optical dipole traps is strongly dependent on the trap anharmonicity.•The anharmonicity prevents energy input beyond certain level.•This energy-input saturation is used for precision measurement of trap parameters.

Parametric excitation of ultracold atomic gases in optical dipole traps strongly depends on the trap anharmonicity. For non-interacting gases, the anharmonicity prevents energy input beyond certain level. We use this as a basis for precision measurement of trap parameters. The frequencies and depth are derived from comparison of the excitation spectrum to models, where the anharmonicity is treated non-perturbatively. Measurements are done for both quantum and classical motion of trapped atoms. For the classical motion, the validity of the model is crosschecked in an independent experiment.