The Bose-Einstein condensate

At about a billionth of a degree above absolute zero, a machine built by the Cold Atoms Group at the Cavendish Laboratory is one of the coolest places on Earth.

The ability to control and cool atoms by laser light has given a completely new twist to the traditional field of atomic physics in recent years

Dr Michael Köhl

According to the laws of thermodynamics, absolute zero (–273.15°C) cannot be reached. However, Dr Michael Köhl’s group in the Department of Physics has developed a laser-based method of cooling that has achieved almost absolute zero. At these ultracool temperatures, atoms trapped in the machine come to a standstill, allowing researchers to study their quantum nature.

‘The ability to control and cool atoms by laser light has given a completely new twist to the traditional field of atomic physics in recent years,’ explained Dr Köhl. ‘Experimentally, it only became achievable a decade ago, but it has initiated a wave of research based on access to a microscopic understanding of quantum degenerate gases.’

The Cold Atoms Group has built a machine in which six interfering laser beams are directed via a small army of lenses through rubidium gas. The laser light slows down the gas atoms, which are then subjected to evaporative cooling in a magnetic trap. For the first time ever in Cambridge, the group has recently demonstrated a Bose–Einstein condensate – essentially, atoms at close to absolute zero that have collapsed into the lowest quantum state.

‘The ultimate controllability of atoms in these states makes us optimistic about studying a whole range of phenomena linked to solid-state physics,’ said Dr Köhl. ‘Such research might provide solutions to unanswered questions in condensed matter physics and high-temperature superconductivity, as well as pave the way for quantum computers of the future.’

For more information, please contact Dr Michael Köhl (mk540@cam.ac.uk).


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