Number 266, April 12, 1996 by Phillip F. Schewe and Ben Stein TAILOR-MADE QUANTUM STATES OF MOTION for a single ion in a trap have been created and observed for the first time. The quantized vibrations of atoms in molecules have been previously observed, but never before have physicists deliberately engineered quantum states of motion in a single atom. Trapping a single beryllium ion in the electric fields of a device known as a Paul trap, Dawn Meekhof (meekhof@boulder.nist.gov) and her colleagues at NIST-Boulder first caught the atom at the center of the trap, where it was free to move in three dimensions. Then they laser-cooled the ion to its lowest-energy state, eliminating the thermal noise that could otherwise obscure signatures of the quantum states the team sought to create. Finally, from the lowest-energy state, the researchers used other lasers to create numerous quantum states specifying the overall motion of the ion. The scientists hope that these and other quantum motional states will provide textbook demonstrations of basic concepts in quantum physics. In a separate experiment, Serge Haroche (haroche@physique.ens.fr) and his colleagues at the Ecole Normale Superieure in France produced the most direct evidence yet of the quantum nature of light by studying how rubidium atoms inside a cavity exchange bundles of energy with a microwave field. (D.M. Meekhof et al. and M. Brune et al., Phys. Rev. Lett., 11 March 1996; for more information, see Science, 5 April 1996; Nature, 4 April 1996; Physics News Update #250) A NEW MATERIAL SHRINKS WHEN HEATED over a wide temperature range, from 0.3 K up to 1050 K. Unlike most materials, which expand when heated, the zirconium tungstate compound (ZrW2O8) made by an Oregon State-Brookhaven collaboration exhibits a negative thermal expansion in three dimensions. Previously known shrinking materials have done so only over a small temperature range, or have shrunk anisotropically; some bakeware ceramics, for example, shrink in one dimension but actually expand in the other two dimensions. The size of the zirconium tungstate structure is closely monitored with sub-angstrom precision, as the temperature is raised, by scattering neutrons (from a Brookhaven reactor) from the sample. An important role for the material would be as a component in composite materials where is to desirable to keep thermal expansion to a minimum. (T.A. Mary et al., Science, 5 April 1996.) THE FIRST X RAYS EVER SEEN COMING FROM A COMET have been observed by the orbiting Rosat x-ray telescope. Without really expecting to see much signal, the Rosat scientists monitored Comet Hyakutake, the brightest comet in more than 20 years, on its swing past Earth a few weeks ago. One provisional explanation for the phenomenon is that x rays from the sun were absorbed by and then reradiated by gas clouds at the comet. Another theory holds that the x rays result from solar wind particles striking the comet. (NASA press release, 27 March.)