Physicists 'flash-freeze' crystal of 150 ions

Physicists at the National Institute of Standards and Technology (NIST) have "flash-frozen" a flat crystal of 150 beryllium ions (electrically charged atoms), opening new possibilities for simulating magnetism at the quantum scale and sensing signals from mysterious dark matter.

Many researchers have tried for decades to chill vibrating objects that are large enough to be visible to the naked eye to the point where they have the minimum motion allowed by quantum mechanics, the theory that governs the behavior of matter at the atomic scale. The colder the better, because it makes the device more sensitive, more stable and less distorted, and therefore, more useful for practical applications. Until now, however, researchers have only been able to reduce a few types of vibrations.

In the NIST experiment, magnetic and electric fields cooled and trapped the ions so that they formed a disc less than 250 micrometers (millionths of a meter) in diameter. The disc is considered a crystal because the ions are arranged in a regularly repeating pattern.

As described in Physical Review Letters, NIST researchers chilled the crystal in just 200 microseconds (millionths of a second) so that each ion had about one-third of the energy carried by a single phonon, a packetofmotional energy in the crystal. This is very close to the amount of energy in the lowest-possible quantum "ground" state for the crystal's so-called "drumhead" vibrations, which are similar to the up-and-down motions of a beating drum.