Macroscopic wave dynamics of bright atomic solitons [electronic resource]
Keywords: Applied Physics

On demand generation of single bright atomic solitons has been demonstrated using ultracold Lithium 7 atoms. These mesoscopic quantum bound states occur in one dimensional systems where attractive forces between particles balances dispersive and diffractive effects. Remarkably, these complicated objects of $N\approx 100$ atoms behave as a single quasiparticle with large effective mass and lifetimes of more than 6 seconds. I present details on our method of single soliton production as well as experiments that probe the quantum nature of these objects: specifically, their preparation in a minimum uncertainty wave packet and experimental signatures indicating the creation of a massive non-local superposition state. In addition, I report on the extension of our methods to multi-soliton production, and present the results of collision experiments with two solitons created at distinct points in a magnetic waveguide. The collisional dynamics include momentum exchange between the two solitons that depends on their relative phase as well as soliton-soliton fusion after multiple collisions. This phenomenology cannot be described by the standard one-dimensional theories used in previous work with atomic soliton trains, and is of interest to future experiments involving solitons for nonlinear atom interferometry and the use of entangled solitons for quantum information. A Bose-Einstein Condensate of Lithium 7 is manipulated for the production of novel quantum many-body states. These include a fragmented state of weakly interacting incoherent solitons, and a pure single bright atomic soliton. In both cases these states result from the weak attraction between Lithium atoms and cooling the particles in a particular magnetic or hybrid magneto-optical potential. The fragmented state is robust under evaporation in a highly anisotropic potential, and while there are potential applications as a bright atomic source with short coherence length, these experiments leave our findings at the stage of observation and basic state description. Production of a pure single bright atomic soliton is more readily interesting for device applications and is studied in greater detail. Considerations for stability and efficient production are elaborated, and an experimental phase diagram is explored. In addition, I report on the lifetime of these states extending into many seconds. Quantum mechanical behavior is observed by studying the momentum spread of a localized wave packet upon release from an optical trap, in accordance with the Heisenberg Uncertainty Principle. Lastly, I report on the extension of our experiments to multi-soliton production. Specifically, collision experiments with two solitons created at distinct points in a magnetic waveguide, separated by tens of microns. Spatial overlap between bright solitary matter-waves is observed for the first time. Additionally, the collisional dynamics include momentum exchange between the two solitons that depends on their relative phase. Lastly, soliton-soliton fusion is observed after multiple collisions. This phenomenology cannot be described by the standard one-dimensional theories used in previous work with atomic soliton trains, and is of interest to future experiments involving solitons for nonlinear atom interferometry and the use of entangled solitons for quantum information.