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“Quantum Whirlpools” Please University of Otago Physicists
Friday, 17 October 2008
Discovering exactly how the Big Bang created the universe may be a step closer – thanks to the combined efforts of physicists from New Zealand, Austraila and the US.
(via University of Otago) Experimental physicists from the University of Arizona worked with theoretical physicists from the University of Queensland, Dr Ashton Bradley (now a Research Fellow at the University of Otago) and Dr Matthew Davis to determine how Bose-Einstein condensates (BECs) form. Their findings are a world first and appear in this week's issue of the prestigious scientific journal, Nature.
A Bose-Einstein condensate is a state of matter formed at ultra-cold temperatures, where atoms behave like waves. It was first predicted by Einstein in 1924; Bose was a young Indian physicist who used the theory to explain certain behaviours of light. Its practical implications are still not fully appreciated, but the development of "atom lasers" may advance the production of nanotechnology and it may also have applications for super-powerful "quantum computers".
Dr Bradley says scientists have been able to make vortices – alignments of atoms forming rotating whirlpools within the otherwise stationary atoms of the BEC – by stirring BECs. But, until now, they had only suspected that vortices may form spontaneously under the right conditions. For years, physicists have speculated about the possibility of vortices being created as a BEC is born.
"Many people still thought that vortices would not be formed spontaneously, because vortices are quite energetic compared to the ground state of the system." The Arizona-Queensland collaboration has been able to show that vortices spontaneously appear between 25 to 50 per cent of the time.
Dr Bradley says that, by quantifying the occurrence of vortex formation in BECs, physicists understand a little more about the behaviour of the atoms in other phase transitions, such as the emergence of structure in the universe after the Big Bang.
"It's something people have been trying to understand for a long time."
Dr Bradley has just joined the University of Otago's Jack Dodd Centre for Quantum Technology directed by Professor Crispin Gardiner. The Jack Dodd Centre is recognised as a leader in ultra-cold atoms research internationally.
The Nature paper has significance for the Jack Dodd Centre, as the theory draws on 12 years' combined work between Professor Gardiner, Otago Department of Physics Head Professor Rob Ballagh, and Dr Matthew Davis (a graduate of the University of Otago). This collaboration previously led to the first successful theoretical description of the dynamics of BEC formation seen in experiments, and provided the foundation for the theory of spontaneous vortices.
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