Optics pioneers win Nobel Prize

17 Jun 2002

US researchers receive recognition for groundbreaking work in atom optics.

Wolfgang Ketterle of the Massachusetts Institute of Technology (MIT) and Eric Cornell and Carl Wieman of the Joint Institute for Laboratory Astrophysics (JILA) in Boulder, Colorado, US, have been awarded this year's Nobel Prize for Physics. They share the prize for "the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates".

Achieving a Bose-Einstein condensate (BEC) of atoms is the first step in an emerging branch of optics called atom optics. Just as light waves contain photons, matter waves contain atoms. The field of atom optics aims to use these matter waves in studies that mirror those already performed using light.

For example, atom interferometers will be developed based on the same principles as today's standard interferometers which use light waves. Other applications in this area include the development of atom lasers, atomic clocks and measuring the acceleration due to gravity.

A BEC is a group of atoms that have been cooled to approximately 50 billionths of a degree above absolute zero. This is achieved in two stages.

The first stage is laser cooling, in which a tunable laser is used to reduce the temperature of the atom ensemble to the order of microkelvin by reducing the speed to the atoms. The second stage is magnetic cooling, in which magnetic fields are applied around the atom cloud, allowing the hottest atoms to escape and reducing the overall temperature of the ensemble to the nanokelvin regime required for BEC.

Cornell, Wieman and colleagues in JILA produced the first BEC in an ultracold gas of rubidium atoms in 1995. Later that year Ketterle and co-workers at MIT achieved condensation in a gas of sodium atoms. Since then there has been an explosion of interest in Bose-Einstein condensation as physicists have probed the properties of this unique state of matter.