Number 278 (Story #2), July 8, 1996 by Phillip F. Schewe and Ben Stein MINIMAL ENERGY REQUIREMENTS IN COMMUNICATIONS. In 1948, information-theory pioneer Claude Shannon showed that sending messages through conventional systems (such as the movement of electrons down a copper wire) without errors requires adding enough energy to the signal to make it roughly as strong as the amount of noise present. This may be true for most communications channels but not for all, IBM physicist Rolf Landauer (914-945-2811) says. He points out that some communication mechanisms could be more robust in weathering a noisy environment. For example, a "bistable" system, such as an ammonia (NH3) molecule in which the nitrogen molecule can pop out of the plane in one direction or the other (representing, say, a 0 or a 1 binary bit), is resistant to noise. Landauer argues that if, furthermore, the system carefully avoids throwing out any data, by "recycling" bits, it might be possible to transmit data with no energy loss at all. Landauer's argument builds on his own work in the 1960s and that of IBM physicist Charles Bennett who previously suggested that under certain conditions the computation process itself can proceed without energy dissipation. (As circuits shrink and speeds increase, the flow of energy and especially the dissipation of heat will someday become important factors in the design of new computers.) Although Landauer admits that implementing his proposed scheme may be impractical, his argument is intended to show that no fundamental limits of minimum energy expenditure for communication necessarily exist. (Rolf Landauer, Science, 28 June 1996.)