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Published Online January 2, 2003
Science DOI: 10.1126/science.1078955

Reports

Submitted on October 1, 2002
Accepted on December 16, 2002

Extracting Work from a Single Heat Bath via Vanishing Quantum Coherence

Marlan O. Scully 1, M. Suhail Zubairy 2, Girish S. Agarwal 3, Herbert Walther 4

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

We here present a new kind of 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 in which we operate; and the heat bath is essentially thermal. However, the phase {phi}, associated with the atomic coherence, provides a new control parameter which can be varied to increase the temperature of the radiation field, and 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 which are not possible in a classical engine.




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