Phase shifts due to atom-surface interaction

Several atom optics experiments have studied how atom-surface interactions affect the propagation of atom waves. However, none of these experiments directly measure the phase shift of atom waves due to interaction with a surface. For example, experiments with atoms transmitted through a cavity [1, 2], atoms diffracted from a material grating [3–6], atoms reflecting from surfaces [7– 10], atoms reflecting from evanescent waves near surfaces [11–13], and atoms trapped near surfaces [? ? ] all monitor how surfaces affect the atom probability density, |ψ|2, in various trajectories. Even with interferometers that use nanostructures [14–18], the predicted phase shifts due to interaction with a surface are not directly observable because there is no absolute reference phase for the interference fringes. Here we compare the interference patterns of four separate atom interferometers and detect a phase difference that we attribute to atom-surface interactions. The interferometers shown in Fig. 1 are obtained by far-field diffraction of a single atom beam by nanofabricated gratings. A single one of these diamond-shaped interferometers has been used for numerous experiments [19], but this is the first use of multiple atom interferometers formed by the same nanostructures.