Scientists have cooled gas to the quietest state ever achieved, and the feat could allow them to detect faint quantum effects in "noisier" gases.
The gas's temperature of a billionth of a degree above absolute zero is twice as high as the lowest entropy (noise )ever measured, but a record low temperature doesn't necessarily mean the least noisy, the University of California, Berkeley reported.
"This 'lowest entropy' or 'lowest noise' condition means that the quantum gas can be used to bring forth subtle quantum mechanical effects which are a main target for modern research on materials and on many-body physics," said co-author Dan Stamper-Kurn, a UC Berkeley professor of physics. "When all is quiet and all is still, one might discern the subtle music of many-body quantum mechanics."
The gas was chilled 50 times lower than the temperature at which quantum statistical effects occur, and observed the "superfluid" behavior that occurred. At these temperature there were low-energy excitations that were deemed to be sound waves.
"Temperature generates something like a constant rumble of sound in the gas, and the entropy is like a count of how many sound-wave excitations remain. The colder a gas becomes, the less entropy it has and the quieter it is," Stamper-Kurn said.
The quantum gas was made up of about a million rubidium atoms trapped by a beam of light. These atoms were then isolated in a vacuum and cooled to their lowest energy state. Being able to manipulate these types of gases could allow researchers to study quantum systems that could lead to breakthroughs in quantum magnets, quantum computers, and high-temperature superconductors.
"One of the holy grails of modern physics is to understand these exotic materials well enough to design one that is superconducting without requiring any cooling at all," said UC Berkeley graduate student Ryan Olf. "By studying the properties of low-entropy gases in various configurations, our community of researchers hope to learn what makes these fascinating materials work the way they do."
The findings were published in a recent edition of the journal Nature Physics.
