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Science

A Bose-Einstein Condensate of Metastable Atoms

A. Robert, O. Sirjean, Antoine Browaeys, J. Poupard, S. Nowak, Denis Boiron, Christoph Ira Westbrook, Alain Aspect

Published Apr 20, 2001• 345 citations
Publisher

Abstract

We report the realization of a Bose-Einstein condensate of metastable atoms (helium in the lowest triplet state). The excitation energy of each atom with respect to the ground state is 20 electron volts, but inelastic processes that would destroy the sample are suppressed strongly enough in a spin-polarized sample to allow condensation. Our detection scheme takes advantage of the metastability to achieve detection of individual atoms as well as of the decay products of inelastic processes. This detection opens the way toward new studies in mesoscopic quantum statistical physics, as well as in atomic quantum optics.

DOI
10.1126/science.1060622

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We report the realization of a Bose-Einstein condensate of metastable atoms (helium in the lowest triplet state). The excitation energy of each atom with respect to the ground state is 20 electron volts, but inelastic processes that would destroy the sample are suppressed strongly enough in a spin-polarized sample to allow condensation. Our detection scheme takes advantage of the metastability to achieve detection of individual atoms as well as of the decay products of inelastic processes. This detection opens the way toward new studies in mesoscopic quantum statistical physics, as well as in atomic quantum optics.
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We report the realization of a Bose-Einstein condensate of metastable helium-444 atoms (4He^{4}\mathrm{He}4He∗{}^{*}∗) in an all-optical potential. Up to 1010105{}^{5}5 spin-polarized 4He^{4}\mathrm{He}4He∗{}^{*}∗ atoms are condensed in an optical dipole trap formed from a single, focused, vertically propagating far-off-resonance laser beam. The vertical trap geometry is chosen to best match the resolution characteristics of a delay-line anode microchannel plate detector capable of registering single He∗{}^{*}∗ atoms. We also confirm the instability of certain spin-state combinations of 4He^{4}\mathrm{He}4He∗{}^{*}∗ to two-body inelastic processes, which necessarily affects the scope of future experiments using optically trapped spin mixtures. In order to better quantify this constraint, we measure spin-state-resolved two-body inelastic loss rate coefficients in the optical trap.
In this, the hundredth year since Einstein first postulated the existence of photons, the successful application of wave - particle duality to matter has seen an explosion of activity in the field of atom optics and Bose - Einstein condensation (BEC). This article provides a brief introduction to atom optics, illustrated with applications taken from experiments using helium atoms in long-lived (metastable) excited states. Metastable helium atoms store the greatest amount of energy (∼20 electron volts) in any atomic or molecular system. They behave like nano-hand grenades, making it easy to detect single atoms, opening up promising applications as well as fundamental studies of the quantum statistical properties of atomic systems.
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