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The creation of a new state of matter has won two Americans and a German the 2001 Nobel Prize in Physics.

Their feat, producing a Bose-Einstein condensate (BEC), was achieved in 1995 – over 70 years after Albert Einstein had extended calculations by Satyendra Nath Bose to predict its existence.

In explaining BECs, the prize citation draws an analogy with light. Compared to ordinary light, a laser beam is composed of photons that 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,” reads the citation. “This year’s Nobel Laureates have succeeded – they have caused atoms to ‘sing in unison’.”

The three honoured are Eric Cornell, at JILA and the National Institute of Standards and Technology in Boulder, Colorado, Carl Wieman JILA and University of Colorado in Boulder, and Wolfgang Ketterle, at the Massachusetts Institute of Technology in Cambridge, Massachusetts. They will share the £690,000 prize money.

Cold, very cold

Einstein predicted that if a gas of certain atoms were cooled to 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.

In 1995, Cornell and Wieman succeeded in achieving this extreme state of matter. They produced a pure condensate of about 2000 rubidium atoms at 20 nanokelvin, i.e. 20 billionths of a degree above absolute zero.

Independently, 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 that were allowed to expand into one another, he obtained very clear interference patterns. This showed that the condensate contained entirely co-ordinated atoms.

The new “control” of matter which BECs involves may bring applications in fields from precision measurement to nanotechnology.