http://phys.org/news/2015-10-quantum-thermodynamics.html
What is quantum in quantum thermodynamics? A new study shows that overunity is a quantum effect that is based on coherence and entanglement. Quote: "One important implication of the new results is that quantum effects may significantly increase the performance of engines at the quantum level. While the current work deals with single-particle engines, the researchers expect that quantum effects may also emerge in multi-particle engines, where quantum entanglement between particles may play a role similar to that of coherence."
