Ultra-cold atom clouds have memory

The coldest form of matter ever created just got a little more interesting. In the February 2007 issue of Nature, researchers at Harvard University reported storing a light pulse in an ultra-cold cloud of atoms (known as a Bose-Einstein condensate, or BEC) and then retrieving it from another BEC some distance away. This showed that light can essentially "jump" from one place to another. According to lead author Lene Hau, professor of physics at Harvard University, "by manipulating the matter copy [of the original light pulse], we can process optical information." This finding may have potential applications in developing the next generation of computers known as quantum' computers.

Held at a fraction of a degree above absolute zero (-273.15C or 0K), a BEC is a super-cooled cloud of atoms. In a BEC, all the atoms appear identical and are at the lowest possible energy level. BECs were first predicted by Satyendra Nath Bose and Albert Einstein in 1925. However, experimental evidence of a BEC wasn't found until 1995, when Carl Wieman and Eric Cornell at the University of Colorado at Boulder succeeded in creating the first BEC.

Since then, BECs have been subject to intense research. Now, Hau and her team have shown that it is possible to transfer a signal between two BECs separated by a distance thousands of times greater than the size of each individual atom.

The researchers used laser beams to cool sodium atoms to form the BECs; a technique first developed by Wieman and Cornell. A light pulse was then imprinted on one BEC before being retrieved as a light pulse from another BEC some distance away.

Hau's findings have important implications for the development of quantum computers, which are considered to represent the next generation of computer technology. Quantum computers use quantum bits, or "qubits", to store information, much like conventional computers use the classical bits 0 and 1 to represent data. This research could provide another way of physically representing qubits, i.e. by storing light information in a BEC and retrieving it at another time as required.

Written by Charles Tran

Reviewed by Frances Mao, David Metcalfe

Published by Pooja Ghatalia

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