Direct imaging of the order parameter of an atomic superfluid using matterwave optics

We propose a method to directly measure the complex phase distribution, superfluid density and velocity field in an ultracold atomic superfluid. The method consists of mapping the momentum distribution of the gas to real space using matterwave focusing, and manipulating the amplitude and phase by means of tailor made optical potentials. This makes it possible to find analogues of well-known techniques in optical microscopy such as Zernike phase contrast imaging, dark field imaging and schlieren imaging. Applying these ideas directly at the level of the macroscopic wavefunction of the superfluid will allow visualization of interesting effects such as phase fluctuations and topological defects, and enable measurements of transport properties such as vorticity.