Maxwellian demon

In effect this theorem denies the existence of a perpetual motion machine of the second kind (PMM2), namely, a device acting as a "Maxwellian demon."... 

Starting from a state on the boundary EgAgAg of given energy E, a Maxwellian demon would allow the system to do work only and, therefore, bring it to a state of energy E2 < E. But Figure 1 shows that such a process necessarily implies a decrease of entropy, which is impossible. 

The possibility of a relation between the second law (in the form of the impossibility of a Maxwellian demon) and irreducible dispersions associated with pure states (represented by Heisenberg s uncertainty principle) was suggested by Slater (10). His suggestion was not adopted, however, because Demers (11) proved that dispersions associated with pure states are insufficient to account for the implications of the second law, especially with regard to heavy atoms at low pressures. In the present work, we can relate the second law to quantal dispersions of mixed states because we have accepted the existence of dispersions of mixed states that are irreducible. 

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