Thermodynamics beats single-electron Maxwell demon

Ars Technica : James Clerk Maxwell proposed a thought experiment in which a demon controlled a hatch between adjacent chambers filled with gas. The demon opened the hatch only to allow molecules moving above a certain velocity through, which would make one room warmer and the other cooler. That outcome paradoxically contravenes the laws of thermodynamics. Leo Szilard extended the idea by proposing two pistons, one on either end of a single chamber with a single gas molecule between them; the demon would put a wall between the pistons so that the molecule drove the piston on that side of the wall before the wall was removed and the process repeated. This Szilard engine is useful for relating thermodynamic energy and information. A team of researchers has now created the first functioning Szilard engine using quantum mechanics instead of classical thermodynamics. Szilard’s gas molecule is replaced by an electron, and the wall is replaced by an energy barrier through which the electron can tunnel. The demon was a pair of sensors, one on either side of the barrier, which detected whether the electron was present and applied a voltage to the barrier trapping the electron on one side. It turned out that the energy used to trap the electron matched the energy lost in the heat bath in which the system sits, as predicted by thermodynamics.