Maxwell’s demon can use quantum information to generate work

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Posted December 19, 2013
Maxwell’s demon can use quantum information to generate work
In the quantum information heat engine, the system is attached to the reservoir, and is measured and controlled by the memory consisting of a diatomic molecule with two entangled states. Credit: Park, et al. ©2013 American Physical Society
In theory, Maxwell’s demon can decrease the entropy of a system by opening and closing a door at appropriate times to separate hot and cold gas molecules. But as physicist Leó Szilárd pointed out in 1929, entropy does not decrease in such a situation because the demon’s measurement process requires information, which is a form of entropy. Szilárd’s so-called information heat engine, now called the Szilárd engine (SZE), demonstrates how work can be generated by using information.

In the SZE and other heat engines devised since then, the information that is used to generate work has always been classical information. Now for the first time, physicists have theoretically demonstrated that a heat engine can generate work using purely quantum mechanical information.

The researchers, Jung Jun Park and Sang Wook Kim from Pusan National University in Busan, Korea; Kang-Hwan Kim from the Korea Advanced Institute of Science and Technology (KAIST) in Daejeon, Korea; and Takahiro Sagawa from Kyoto University in Kyoto, Japan, have published their paper on their work in a recent issue of Physical Review Letters.

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