Ultra cold gases present a very rich dynamics driven by quantum physics. The gas vibration modes depend on the atomic interactions and on the detail of the trapping potential. In order to observe these modes, successive images of the moving atomic cloud are taken, directly in the trap. Until now, the resulting pictures were analyzed by fitting the density profiles with a theoretical model. This only gives access to a limited number of parameters, such as the atom number or the cloud size. This approach prevents from getting all the information present in the images. Inspired by a statistical technique already used in biophysics or astronomy, Principal Component Analysis (PCA), the BEC group at LPL has succeeded in observing for the first time the real shape of all the vibration modes simultaneously excited in an ultra cold gas, as well as their frequencies.
This work is published as a Fast Track Communication in New Journal of Physics. See also the video abstract.
Caption: The scissors mode, corresponding to an oscillation of the atomic cloud around its long axis, is clearly visible on this component.