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Science 7 February 2003:
Vol. 299. no. 5608, pp. 841 - 842
DOI: 10.1126/science.1080886
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Perspectives

PHYSICS:
Coherent Power Booster

Heiner Linke

According to the Second Law of Thermodynamics, a heat engine requires two heat baths to operate-a warm source of heat and a cooler dump for waste heat. In apparent violation of this law, Scully et al. propose a heat engine that uses quantum coherence to extract work from a single, warm gas. In his Perspective, Linke explains that the Second Law is not violated, because the power extracted from the bath is smaller than that required to achieve coherence. By combining quantum mechanics with traditional heat engines, the efficiencies of various kinds of motors could be enhanced.

The author is in the Physics Department and Materials Science Institute, University of Oregon, Eugene, OR 97403, USA. E-mail: linke{at}uoregon.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)