Tiny Fridge Gets Near Absolute Zero
By Laura Sanders, Science News August 30, 2010
Annoyingly tiny fridges may not be restricted to hotels or dorm rooms much longer. A new study proposes a way to construct the smallest refrigerator yet, based on just a few particles and capable of cooling to near absolute zero.
The study, which will appear in an upcoming issue of Physical Review Letters, pushes the limits of how small a cooling device can get and still remain functional.
“When thermodynamics was first invented, it was applied to big, steam engine sorts of things,” says physicist Tony Short of the University of Cambridge in England, who was not involved in the study. “The fact that you can bring the ideas all the way down to individual quantum systems of tiny dimensions and the same basic ideas still work is quite nice.”
Study coauthors Noah Linden, Sandu Popescu and Paul Skrzypczyk, all of the University of Bristol in England, propose a cooling scheme that relies on three linked qubits — particles that can exist in one of two states. Two of these qubits make up the refrigerator and would be held in two different heat baths: one very hot and one near room temperature. The third qubit is the object to be cooled. Because these qubits share a quantum connection, they can influence one another. So, as the hottest qubit absorbs energy from its toasty bath, it triggers the tepid qubit to siphon energy off the third qubit, cooling it. This extra energy dissipates off the second qubit in the same way the coil at the back of a refrigerator in the kitchen emits heat.
In their calculations, the physicists found that as the bath of the hottest qubit got hotter, the cooling ability of the fridge got better. And in principle, as long as the heat bath stays hot, the system can run forever. “Once you set it up, it just sits there, gently cooling away,” Linden says.
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