Quantum interactions of single atoms on huge length scales

Observing the interaction of neutral atoms or molecules in space and time is extremely difficult, since such interactions only occur on ultra small length scales (0.1 nm), and ultra fast time scales. A team of researchers at the University of Amsterdam, the FOM Institute for Atomic and Molecular Physics (AMOLF) and Auburn University have recently for the first time shown that they can record a 'movie' of such interactions by magnifying the length scale of the interaction to a spectacular 50 microns (the thickness of a hair, or a million times the size of an atom) and slowing down the time scale at which such 'dipole-dipole' interactions occur by 10,000 times. There are two essential tricks: the first is to magnify the atoms themselves by exciting the outer electron to an orbit very far removed from the atomic nucleus.

The second trick is to cool the atoms to ultra low temperatures, so that they don't move during the recording of the movie. The experiment reported by the authors provides an interesting model system for resolving 'dipole-dipole' interactions simultaneously in time and space. 'Dipole-dipole' interactions are of fundamental interest, and are ubiquitous in for instance biophysics, plasmonics and quantum optics. Furthermore, the experiment is a first step towards realizing a quantum computing system in which neutral atoms act as quantum bits of information, and for which researchers can resolve the coherent transport of quantum information in space and time. On June 20th, the researchers published their results in the leading scientific journal Physical Review Letters.

C. S. van Ditzhuijzen, A. F. Koenderink, J. V. Hernández, F. Robicheaux, L. D. Noordam, and H. B. van den Heuvell.
Spatially Resolved Observation of Dipole-Dipole Interaction between Rydberg Atoms.

Physical Review Letters 100 (2008) 243201

(July 2008)