Maxwell’s Demon, Szilard’s Engine and Quantum Measurements

  • W. H. Zurek
Part of the NATO ASI Series book series (NSSB, volume 135)


We propose and analyze a quantum version of Szilard’s “one-molecule engine.” In particular, we recover, in the quantum context, Szilard’s conclusion concerning the free energy “cost” of measurements: ΔF⩾kBTln2 per bit of information.


Density Matrix Mutual Information Quantum Measurement External Observer Entropy Increase 
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Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • W. H. Zurek
    • 1
    • 2
  1. 1.Theoretical AstrophysicsLos Alamos National LaboratoryLos AlamosUSA
  2. 2.Institute for Theoretical PhysicsUniversity of CaliforniaSanta BarbaraUSA

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