Ultracold science finds new method to get even colder
Achieving such temperatures is necessary to study fundamental properties of matter and the strange effects caused by quantum mechanics.
The new method relies on "optical lattices" of atoms from which only the hottest atoms are selectively removed.
The approach, reported in Nature, may be well-suited to create memory for future quantum computers.
The limits of low temperature have been constantly pushed in recent years, and the current best lies somewhere in the nanoKelvin regime - that is, within just billionths of a degree of "absolute zero" at zero Kelvin or -273.15C.
That ultimate limit is set formally as the lowest possible entropy, or disorder, that is achievable.
Optical lattices are an ideal system in which to attain temperatures ever nearer that limit. The peaks and troughs of intensity in crossed beams of light form a kind of "egg-crate" structure in which atoms are inclined to remain in the troughs - a point of lowest energy.
As the atoms are added to each trough - or each point in the lattice - it becomes more difficult to add another, in a situation called a blockade.
But researchers from Harvard University have invented a modification to this effect called orbital exchange blockade.
It is a way to cool these assemblages of atoms that could be extended to the picoKelvin regime: within trillionths of a degree of the coldest possible temperature.
The team carefully adjusted the intensity of the crossed light beams. The trick was to do so in such a way that only the most energetic atoms in each lattice site absorbed energy from the light fields, becoming more energetic again; Kazinform cites BBC.
To learn more go to www.bbc.co.uk