Noisy snapshots show quantum weirdness

Researchers from the University of Colorado have devised a relatively simple way to detect a pair of entangled, or linked atoms.

The properties of entangled atoms, including magnetic orientation, or spin, remain linked regardless of the distance between the atoms.

The detection ability advances quantum computer and quantum communications research. Quantum computers and communications equipment use properties of particles like atoms to store, manipulate and transport information. Entangled particles are well-suited to carry out the basic logic operations of quantum computers and to teleport particles. Quantum computers could, in theory, solve certain large problems orders of magnitude faster than classical computers.

Key to the researchers' method is it does not involve the difficult task of detecting single atoms. Instead, the method measures noise -- fluctuations in images of clouds of atoms. The method also gives researchers a useful tool for studying all kinds of atomic phenomena including ultracold gas clouds, where it is difficult to identify individual atoms.

To measure the image fluctuations the researchers cooled atoms confined to an optical trap, used a magnetic field to coax pairs of atoms to form molecules, then used a different magnetic field to break up the molecules, leaving the pairs entangled and flying apart in opposite directions.

They then fired a laser at the atom cloud and recorded the light scattering off the atoms with a digital camera. Identical patterns in the digital images revealed the entangled pairs.

Researchers generally agree that practical quantum computers are one to two decades away. The work appeared in the March 25, 2005 issue of Physical Review Letters (Probing Pair-Correlated Fermionic Atoms to Correlations and Atom Shot Noise).