A quantum - mechanical Maxwell ’ s demon †

A Maxwell’s demon is a device that gets information and trades it in for thermodynamic advantage, in apparent (but not actual) contradiction to the second law of thermodynamics. Quantum-mechanical versions of Maxwell’s demon exhibit features that classical versions do not: in particular, a device that gets information about a quantum system disturbs it in the process. In addition, the information produced by quantum measurement acts as an additional source of thermodynamic inefficiency. This paper investigates the properties of quantummechanical Maxwell’s demons, and proposes experimentally realizable models of such devices. † This work supported in part by grant # N00014-95-1-0975 from the Office of Naval Research, and by ARO and DARPA under grant # DAAH04-96-1-0386 to QUIC, the Quantum Information and Computation initiative.