The second law of thermodynamics should make that impossible, but how? That question has stymied physicists and provoked debate for a century and a half. The experiments in this thesis confirm a hypothesis proposed by Rolf Landauer over fifty years ago: that Maxwell's demon would need to erase information, and that erasing information-resetting the measuring device to a standard starting state-requires dissipating as much energy as is gained.

 For his thesis work, the author used a "feedback trap" to study the motion of colloidal particles in "v