Monday, December 12, 2005

"QUANTUM: Lab advances boost quantum info systems"

Recent developments bode well for comprehensive quantum information systems. Work at labs in Colorado and Austria has increased the ability to store quantum states on groups of atoms, and researchers in Georgia have found a way to transfer quantum states over networks. Two groups-at the National Institute of Standards and Technology (NIST; Boulder, Colo.) and at the University of Innsbruck's Institute of Theoretical Physics-have separately pushed up the number of ions that can exist in a simultaneous superposition of states. Just as NIST researchers were reporting a successful experiment observing six rubidium ions in a synchronized state of superposition (see Nov. 28, page 12), the Innsbruck group announced the observation of eight calcium ions in a magnetic ion trap. Previously, quantum computing research had established quantum entanglement in five photons. Meanwhile, a team at the Georgia Institute of Technology has found a way to build quantum state "repeaters"-systems that regenerate a quantum state being transmitted over a network-which would enable larger quantum networks to be built. The first application of the development will likely be in emerging quantum encryption systems that operate over optical networks. In theory, quantum repeaters could exchange secure encryption keys. By demonstrating the temporary storage and retrieval of quantum information from a cloud of rubidium atoms, the Georgia Tech researchers have verified the possibility of building such systems.