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Department of Physics

A phase microscope for quantum gases

Scheme of the phase microscope. © Christof Weitenberg
Scheme of the phase microscope: a phase imprinting in Fourier space of a matter-wave imaging maps initial phase fluctuations onto density fluctuations.
We have realized a microscope that measures phase profiles of a Bose-Einstein condensate in an optical lattice with single-site resolution.

Coherence properties are central to quantum systems and are at the heart of phenomena such as superconductivity. Here we study coherence properties of an ultracold Bose gas in a two-dimensional optical lattice across the thermal phase transition. To infer the phase coherence and phase fluctuation profile, we use direct matter-wave imaging of higher Talbot revivals as well as a new phase microscope based on a site-resolved mapping of phase fluctuations to density fluctuations during matter-wave imaging. We observe the algebraic decay of the phase correlations in the superfluid phase and a linear temperature increase of the exponent. These techniques will also allow studying coherence properties in strongly-correlated quantum systems with full spatial resolution.

The preprint is available here.