Physical Uncertainty and Information

Uncertainties inherent in physical phenomena and structures obscure the physical representation of information. Time-dependent uncertainties in physical parameters are conventionally regarded as noise. Time-independent uncertainties, fixed in the physical structure of the devices used to represent information, although determinable in principle, are in fact unknown to the system designer and play a role in information theory similar to that of conventional noise. Several examples of the way in which power is used in logic and memory devices to overcome the effects of physical uncertainty are presented.