The smallest possible refrigerator

When it comes to refrigerators, size matters. Who hasn't at least once in their life wished for a bigger fridge' However, who can say they've wished for the extreme opposite ' the smallest conceivable one? But this is exactly what experts in quantum mechanics from the University of Bristol have done. It's not a question of engineering, of how small can one build a refrigerator, but about the fundamental limitations that Nature may impose on the size of refrigerators. Is there a minimum size below which no refrigerator can work? The Bristol team - Professor Noah Linden , Professor Sandu Popescu and Paul Skrzypczyk - found there is no minimum size, and, using quantum mechanics, designed what is arguably the smallest possible refrigerator. It works extremely well too: it can cool as close as you like towards absolute zero. One model refrigerator is made from just three two-level quantum systems - the simplest possible physical systems, known as qubits. Two of the qubits make up the refrigerator - one in a hot heat bath, the other in a heat bath at 'room temperature'; the third is the object to be cooled.