Sabine Stock

Interference of an Array of Independent Bose-Einstein Condensates

We have observed high-contrast matter wave interference between 30 Bose-Einstein condensates with uncorrelated phases. Interferences were observed after the independent condensates were released from a one-dimensional optical lattice and allowed to overlap. This phenomenon is explained with a simple theoretical model, which generalizes the analysis of the interference of two condensates.

Observation of Coherent Transients in Ultrashort Chirped Excitation of an Undamped Two-Level System

The effects of coherent excitation of a two-level system with a linearly chirped pulse are studied theoretically and experimentally [in Rb (5s-5p)] in the low field regime. The coherent transients are measured directly on the excited state population on an ultrashort time scale. A sharp step corresponds to the passage through resonance. It is followed by oscillations resulting from interferences between off-resonant and resonant contributions. We finally show the equivalence between this experiment and Fresnel diffraction by a sharp edge.

Observation of Phase Defects in Quasi-Two-Dimensional Bose-Einstein Condensates

We have observed phase defects in quasi-2D Bose-Einstein condensates close to the condensation temperature. Either a single or several equally spaced condensates are produced by selectively evaporating the sites of a 1D optical lattice. When several clouds are released from the lattice and allowed to overlap, dislocation lines in the interference patterns reveal nontrivial phase defects.

Shape oscillation of a rotating Bose-Einstein condensate

We present a theoretical and experimental analysis of the transverse monopole mode of a fast rotating Bose-Einstein condensate. The condensates rotation frequency is similar to the trapping frequency and the effective confinement is only ensured by a weak quartic potential. We show that the non-harmonic character of the potential has a clear influence on the mode frequency, thus making the monopole mode a precise tool for the investigation of the fast-rotation regime.

Quantized vortices in the ideal bose gas: a physical realization of random polynomials.

We propose a physical system allowing one to experimentally observe the distribution of the complex zeros of a random polynomial. We consider a degenerate, rotating, quasi-ideal atomic Bose gas prepared in the lowest Landau level. Thermal fluctuations provide the randomness of the bosonic field and of the locations of the vortex cores. These vortices can be mapped to zeros of random polynomials, and observed in the density profile of the gas.