Splitting and recombination of bright-solitary-matter waves

Bright solitary waves are wavepackets that propagate without dispersion and have been under intense investigation in a variety of settings, including Bose-Einstein condensates (BEC), with a view of realizing a matter-wave interferometer. The authors present experimental and theoretical results on a bright-matter-wave soliton from a BEC, and observe splitting and recombination at a barrier potential enabling them to place constraints on the barrier stability needed to implement soliton interferometry. Atomic Bose-Einstein condensates confined in quasi-1D waveguides can support bright-solitary-matter waves when interatomic interactions are sufficiently attractive to cancel dispersion. Such solitary-matter waves are excellent candidates for highly sensitive interferometers, as their non-dispersive nature allows them to acquire phase shifts for longer times than conventional matter-wave interferometers. In this work, we demonstrate experimentally the splitting and recombination of a bright-solitary-matter wave on a narrow repulsive barrier, realizing the fundamental components of an interferometer. We show that for a sufficiently narrow barrier, interference-mediated recombination can dominate over velocity-filtering effects. Our theoretical analysis shows that interference-mediated recombination is extremely sensitive to the barrier position, predicting strong oscillations in the interferometer output as the barrier position is adjusted over just a few micrometres. These results highlight the potential of soliton interferometry, while putting tight constraints on the barrier stability needed in future experimental implementations.