![]() xii) note that more references have been generated in the 13 years since the volume's first edition than in all years prior to it, extending back over the demon's 120 years of life. In the second edition of their standard compilation of work on Maxwell's demon, Leff and Rex (2003, p. Charles Bennett's recent extension of Landauer's principle to the merging of computational paths fails for the same reasons as trouble the original principle.Ī sizeable literature is based on the claim that Maxwell's demon must fail to produce violations of the second law of thermodynamics because of an inevitable entropy cost associated with certain types of information processing. ![]() The theorizing surrounding Landauer's principle is too fragile and too tied to a few specific examples to support such general exorcism. To exorcise Maxwell's demon one must show that all candidate devices-the ordinary and the extraordinary-must fail to reverse the second law of thermodynamics. They turn out to depend on the illicit formation of a canonical ensemble from memory devices holding random data. General arguments that purport to establish the unconditional validity of the law (erasure maps many physical states to one erasure compresses the phase space) fail. It can be formulated as a precise result in statistical mechanics, but for a restricted class of erasure processes that use a thermodynamically irreversible phase space expansion, which is the real origin of the law's entropy cost and whose necessity has not been demonstrated. Landauer's principle is the loosely formulated notion that the erasure of n bits of information must always incur a cost of k ln n in thermodynamic entropy.
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