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Exciting Rydberg atoms in Bose-Einstein condensates

In the third of a series of Letters on coherent Rydberg excitation of dense ultracold atoms, we report on the investigation of Rydberg atoms in a Bose-Einstein condensate (BEC) [1]. Due to the strong interactions between the Rydberg atoms up to 10000 atoms team up as a so called "super atom" to share a single Rydberg excitation in a coherent way [2]. In another experiment they prove the coherence of the excitation despite strong interactions and investigated dephasing processes [3].

Rydberg atoms are several thousands of times larger than normal atoms. The loosely bound electron is extremely sensitive to electric fields and to other nearby Rydberg atoms. Therefore Rydberg atoms can talk to each other on distances of around 5 micrometers. This is 50 times their own size and half the size of a human red blood cell - huge distances for atoms. At the same time Rydberg atoms can store quantum information by a well protected nuclear spin. That's why they are discussed as a possible system for the implementation of quantum algorithms [4]. Besides this Rydberg atoms in a BEC will be able to model coherent many body physics far from equilibrium and impurities in a quantum gas.

Ultracold Rubidium atoms excited with laserlight (blue and red) to Rydberg states. The picture shows a MOT (hotter than BEC).

See also the press release.

[1]    R. Heidemann, U. Raitzsch, V. Bendkowsky, B. Butscher, R. Löw, T. Pfau,
" Rydberg excitation of Bose-Einstein condensates"
Physical Review Letters in press
arXiv: arXiv:0710.5622 (2007)

[2]    R. Heidemann, U. Raitzsch, V. Bendkowsky, B. Butscher, R. Löw, L. Santos, T. Pfau,
" Evidence for coherent collective Rydberg excitation in the strong blockade regime",
Physical Review Letters 99, 163601 (2007)
arXiv: quant-ph/0701120 (2007) ( link)

[3]    U. Raitzsch, V. Bendkowsky, R. Heidemann, B. Butscher, R. Löw, T. Pfau,
" An echo experiment in a strongly interacting Rydberg gas"
Physical Review Letters in press
arXiv: arXiv:0706.3869 (2007)

[4]    M. D. Lukin, M. Fleischhauer, R. Cote, L. M. Duan, D. Jaksch, J. I. Cirac, and P. Zoller, „ Dipole Blockade and Quantum Information Processing in Mesoscopic Atomic Ensembles“, Physical Review Letters, 87, 037901 (2001)