American Journal of Physics
The problem of Maxwell’s sorting demon traditionally has been studied for the case in which the hot and cold regions differ very little in temperature. In this article a solution is presented for the case in which the temperature difference is great so that the total entropy is lower. Calculations indicate that in this case the demon must use a large number of photons to observe the proper kinds of particles. This causes an increase in entropy which more than offsets the decrease caused by an exchange of particles.
Rex, A F. "The Operation of Maxwell’s Demon in a Low Entropy System." American Journal of Physics. 55.4 (1987). Print.