  We demonstrate tomographic reconstruction of the phase space distribution of
atoms oscillating in a harmonic trap with weak potential corrugation caused by
nanoscale imperfections in an atom chip. We find that deformations in these
distributions are highly sensitive to anharmonic components of the potential.
They are explained in terms of angular velocity dispersion of isoenergetic
phase space trajectories. We show that the method is applicable for probing
classical and quantum dynamics of cold atoms, and we note its importance for
future technological applications.
