Information, Noise, and Energy Dissipation: Laws, Limits, and Applications

Abstract

This Chapter addresses various subjects, including some open questions related to energy dissipation, information and noise that are relevant for nano-and molecular electronics. The object is to give a brief and coherent presentation of the results of a number of recent studies of ours. 1. Energy dissipation and miniaturization It has been observed, in the context of Moore's law, that the power density dissi-pation of microprocessors keeps growing with increasing miniaturization [1-4], and quantum computing schemes are not principally different [5,6] for general-purpose computing applications. However, as we point out in Section 2 below and seemingly in contrast with the above statements, the fundamental lower limit of energy dissipation of a single bit-flip event (or switching event) is independent of the size of the system. Therefore the increasing power dissipation may stem from the following practical facts [1-4]: • A larger number of transistors on the chip, contributing to a higher number of switching events per second; • lower relaxation time constants with smaller elements, allowing higher clock frequency and the resulting increased number of switching events per second; • increasing electrical field and current density, because the power supply voltage is not scaled back to the same extent as the device size; and • enhanced leakage current and related excess power dissipation, caused by an exponentially increasing tunneling effect associated with decreased insulator thickness and increased electrical field.