Manipulation Of Bose-Einstein Condensates Research Articles

Optimal nonlinear coherent mode transitions in Bose-Einstein condensates utilizing spatiotemporal controls

Bose-Einstein condensates (BECs) offer the potential to examine quantum behavior at large length and time scales, as well as forming promising candidates for quantum technology applications. Thus, the manipulation of BECs using control fields is a topic of prime interest. We consider BECs in the mean field model of the Gross-Pitaevskii equation (GPE), which contains linear and nonlinear features, both of which are subject to control. In this work we report successful optimal control simulations of a one dimensional GPE by modulating the linear and nonlinear terms to stimulate transitions into excited coherent modes. The linear and nonlinear controls are allowed to freely vary over space and time to seek their optimal forms. The determination of the excited coherent modes targeted for optimization is numerically performed through an adaptive imaginary time propagation method. Numerical simulations are performed for optimal control of mode-to-mode transitions between the ground coherent mode and excited modes of a BEC trapped in a harmonic well. The results show greater than 99% success for nearly all trials utilizing reasonable initial guesses for the controls, and analysis of the optimal controls reveals primarily direct transitions between initial and target modes. The success of using solely the nonlinearity term as a control opens up further research toward exploring novel control mechanisms inaccessible to linear Schr\"odinger-type systems.

Matter-wave soliton control in optical lattices with topological dislocations

We address the concept of guiding and transporting matter-wave solitons along the channels of optical lattices made by interference patterns of beams containing topological wavefront dislocations. The local lattice distortions that occur around the dislocations cause solitons to move along reconfigurable paths, a phenomenon that may be used for controlled all-optical manipulation of Bose-Einstein condensates. Multiple dislocations form traps that can capture and hold moving solitons. We also show that suitable lattice topologies may be used to explore matter-wave soliton collisions and interactions in a confined reconfigurable environment.

Optically tunable hollow Gaussian beams with thin metal films

We report the formation of optically tunable, smooth hollow beams by reflection of a TEM00 Gaussian beam off a metal thin film. Hollow (doughnutlike) beams (HBs) with controllable profiles are created by a phase distortion at the surface. Two regimes of operation are observed: Below a certain power threshold, the HB formation is reversible and optically tunable on a time scale of milliseconds; above that threshold, alterations on the film surface make the effect permanent. Optical control of the HB shape is demonstrated by tuning the power of a second beam. High stability in the radial intensity profile and the possibility of adjusting the spatial distribution and aspect ratios make this technique promising for applications such as atom trapping and manipulation of Bose-Einstein condensates.

UHV-compatible magnetic material for atom optics

Magnetic videotape is of great interest for trapping and guiding cold atomic vapors, but was hitherto considered unsuitable for manipulating Bose–Einstein condensates (BEC) because of the presumed evolution of gas under vacuum. We have studied the outgassing in vacuum of the most promising tape, Ampex 398 Betacam SP. We find that after cleaning in ethanol and baking for 200 h at 100 °C the magnetic patterns are undisturbed and the outgassing is remarkably small: 4×10-10 Torr l s-1cm-2, due mostly to hydrogen. This makes the tape exceedingly attractive for manipulation of BEC.

Manipulation of Bose-Einstein condensates by dipole potentials

The coherent manipulation of Bose-Einstein condensates by far blue detuned dipole potentials is discussed. ‘Classical’ atom optical elements, such as mirrors and waveguides, are realized and the dynamics of coherent matter waves interacting with these elements is investigated. The local manipulation of the phase of the condensate wavefunction by temporally applied dipole potentials represents a powerful tool for the design of matter waves. We use this method in particular for the creation of dark solitons in Bose-Einstein condensates and study their dynamics.

Cooling, Trapping and Manipulation of Neutral Atoms and Bose-Einstein Condensates by Electromagnetic Fields

We give a general discussion of the mechanical effects of light, and of laser cooling and trapping techniques. This is followed by a description of experiments in the manipulation of Bose-Einstein condensates with optical laser pulses.