A soliton is a wave that doesn’t disperse or spread out as it propagates. Here is a video of solitons in water:
We make a soliton out of a cold gas of Rubidium-85 atoms by tuning their collisional properties. By cold I mean billionths of a degree above absolute zero. Instead of being confined in a giant fish tank like in the video above, they are confined in a tube of light.
Next, we create a two-path interferometer from this cloud of atoms, and the atoms interfere with themselves via quantum mechanics.
It turns out that a soliton interferometer (with just the right value of attractive collisional properties) has a stronger interference fringe than either a repulsive or non-interacting cloud of atoms put through the same interferometer.
Here’s the full abstract.
We present the first realisation of a solitonic atom interferometer. A Bose-Einstein condensate of 10,000 atoms of rubidium-85 is loaded into a horizontal optical waveguide. Through the use of a Feshbach resonance, the s-wave scattering length of the 85Rb atoms is tuned to a small negative value. This attractive atomic interaction then balances the inherent matter-wave dispersion, creating a bright solitonic matter wave. A Mach-Zehnder interferometer is constructed by driving Bragg transitions with the use of an optical lattice co-linear with the waveguide. Matter wave propagation and interferometric fringe visibility are compared across a range of s-wave scattering values including repulsive, attractive and non-interacting values. The solitonic matter wave is found to significantly increase fringe visibility even compared with a non-interacting cloud.
arXiv Preprint Full text on PRL website Download article here