  Landauer (1961) investigated the question of what are the physical limitations on building a device to implement a computation. At the time he wrote, an influential body of work had been developed, by Brillouin (1951, 1956), Gabor (1964) and Rothstein (1951), arguing that the acquisition of information through a measurement required a dissipation of at least kT  ln 2 energy for each bit of information gathered. von Neumann (1949) had also suggested on the basis of Szilard's work, that every act of information processing was necessarily accompanied by this level of energy dissipation.