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Originally published in Science Express on 2 January 2003
Science 7 February 2003:
Vol. 299. no. 5608, pp. 862 - 864
DOI: 10.1126/science.1078955
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Reports

Extracting Work from a Single Heat Bath via Vanishing Quantum Coherence

Marlan O. Scully,12 M. Suhail Zubairy,13 Girish S. Agarwal,14 Herbert Walther2

We present here a quantum Carnot engine in which the atoms in the heat bath are given a small bit of quantum coherence. The induced quantum coherence becomes vanishingly small in the high-temperature limit at which we operate and the heat bath is essentially thermal. However, the phase phi , associated with the atomic coherence, provides a new control parameter that can be varied to increase the temperature of the radiation field and to extract work from a single heat bath. The deep physics behind the second law of thermodynamics is not violated; nevertheless, the quantum Carnot engine has certain features that are not possible in a classical engine.

1 Department of Physics and Institute for Quantum Studies, Texas A&M University, TX 77843, USA.
2 Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
3 Department of Electronics, Quaid-i-Azam University, Islamabad, Pakistan.
4 Physical Research Laboratory, Navrangpura, Ahmedabad-380009, India.

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