Schematic of the information-energy conversion with a macroscopic demon and a microscopic system Szilard engine as an example). The Szilard-engine can achieve the 100% conversion rate from information to energy
Nature Physics – Experimental demonstration of information-to-energy conversion and validation of the generalized Jarzynski equality Scientists in Japan are the first to have succeeded in converting information into free energy in an experiment that verifies the “Maxwell demon” thought experiment devised in 1867.
In 1929, Leó Szilárd invented a feedback protocol in which a hypothetical intelligence—dubbed Maxwell’s demon—pumps heat from an isothermal environment and transforms it into work. After a long-lasting and intense controversy it was finally clarified that the demon’s role does not contradict the second law of thermodynamics, implying that we can, in principle, convert information to free energy. An experimental demonstration of this information-to-energy conversion, however, has been elusive. Here we demonstrate that a non-equilibrium feedback manipulation of a Brownian particle on the basis of information about its location achieves a Szilárd-type information-to-energy conversion. Using real-time feedback control, the particle is made to climb up a spiral-staircase-like potential exerted by an electric field and gains free energy larger than the amount of work done on it. This enables us to verify the generalized Jarzynski equality, and suggests a new fundamental principle of an ‘information-to-heat engine’ that converts information into energy by feedback control.