April 2011

Abstracts of the QSIT Lunch Seminar, April 7, 2011

Interferometric Measurement of Local Spin-Fluctuations in a Quantum Gas

Jakob Meineke, Quantum Optics Group, ETH Zurich

Current efforts in the field of ultracold quantum gases are directed towards the investigation of their magnetic properties. We present a quantum-limited interferometric method and use it to measure the spin-fluctuations of a trapped Fermi gas. This allows us to measure the magnetic susceptibility of a weakly interacting Fermi gas as a function of temperature and to show the presence of entanglement in a strongly interacting gas.

Spin-Squeezing a Bose-Einstein Condensate on an Atom Chip

Roman Schmied*, Quantum Atom Optics Lab, University of Basel

At the core of all quantum information technology lies the deterministic and robust generation of entanglement. Our group has succeeded in generating multiparticle entangled states of trapped atoms for the first time, by spin-squeezing a two-component Bose-Einstein condensate of 87Rb atoms [1]. This was achieved by applying a micrometer-scale internal-state dependent potential to the atoms, which results in internal-state dependent collisional phase shifts. We have developed a novel tomographic method for analyzing and visualizing these experimental states through the spherical Wigner function [2].

References:

[1] M. Riedel, P. Böhi, Y. Li, T. W. Hänsch, A. Sinatra, and P. Treutlein, Atom-chip-based generation of entanglement for quantum metrology, Nature 464, 1170 (2010)
[2] R. Schmied and P. Treutlein, Tomographic reconstruction of the Wigner function on the Bloch sphere, arXiv:1101.4131 (2011)

*Co-authors: Max F. Riedel, Pascal Böhi, Caspar Ockeloen, and Philipp Treutlein, Department of Physics, University of Basel, Switzerland