Maxwell's demon, information as thermodynamic resource, and Landauer's principle
The Szilard engine extracts W = kT ln 2 work per bit of information gained by measuring a particle's location. This appears to violate the 2nd law — but Landauer's erasure principle resolves the paradox: erasing one bit requires dissipating ≥ kT ln 2 heat, exactly canceling the work extracted.