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NOBEL PRIZE for physics 2001
 New
State of Matter Revealed: Bose-Einstein Condensate
Eric A. Cornell JILA and National Institute of Standards and
Technology (NIST), Boulder, Colorado, USA,
Wolfgang Ketterle Massachusetts Institute of Technology (MIT),
Cambridge, Massachusetts, USA,
Carl E. Wieman JILA and University of Colorado, Boulder, Colorado,
USA,
A laser beam differs from the light from an ordinary light
bulb in several ways. In the laser the light particles all
have the same energy and oscillate together. To cause matter
also to behave in this controlled way has long been a challenge
for researchers.
This year's Nobel Laureates have succeeded – they have caused
atoms to "sing in unison" – thus discovering a new state of
matter, the Bose-Einstein condensate (BEC). In 1924 the Indian
physicist Bose made important theoretical calculations regarding
light particles. He sent his results to Einstein who extended
the theory to a certain type of atom. Einstein predicted that
if a gas of such atoms were cooled to a very low temperature
all the atoms would suddenly gather in the lowest possible
energy state. The process is similar to when drops of liquid
form from a gas, hence the term condensation. Seventy years
were to pass before this year's Nobel Laureates, in 1995,
succeeded in achieving this extreme state of matter.
Cornell and Wieman then produced a pure condensate
of about 2 000 rubidium atoms at 20 nK (nanokelvin), i.e.
0.000 000 02 degrees above absolute zero.
Independently of the work of Cornell and Wieman, Ketterle
performed corresponding experiments with sodium atoms. The
condensates he managed to produce contained more atoms and
could therefore be used to investigate the phenomenon further.
Using two separate BECs which were allowed to expand into
one another, he obtained very clear interference patterns,
i.e. the type of pattern that forms on the surface of water
when two stones are thrown in at the same time. This experiment
showed that the condensate contained entirely co-ordinated
atoms.
Ketterle also produced a stream of small "BEC drops" which
fell under the force of gravity. This can be considered as
a primitive "laser beam" using matter instead of light. It
is interesting to speculate on areas for the application of
BEC. The new "control" of matter which this technology involves
is going to bring revolutionary applications in such fields
as precision measurement and nanotechnology.
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