Minimum Energy of Computing, Fundamental Considerations

In the last forty years the progress of the semiconductor industry has been driven by its ability to cost-effectively scale down the size of the CMOS-FET [1] switches, the building block of present computing devices, and this has provided continuing increases in computing capa‐ bility. However, this has been accompanied by a continuing increase in energy consumption and heat generation up to a point where the power dissipated in heat during computation has become a serious limitation [2, 3]. The energetics issues of current and future computation raises a question of the ultimate energy efficiency of computation that is reminiscent of the Carnot limit for the efficiency for heat engines [4]. It should be noted that the entire discipline of thermodynamics emerged from the practical need to increase the efficiency of utility heat engines. Innovations in steam engines and internal combustion engines have been driven by the need to more closely approach the ideal limit of a Carnot engine. Today, approximately 200 years after the work of Carnot, the problem of understanding the efficiency of generalized energy generators remains, although today the object of interest not only includes large power plants but also small scale devices and systems for information processing. In fact, one can view information processor as a computing engine that transforms incoming energy flow into useful work and also produces some heat [5].