COMPUTING IN THE 21ST-CENTURY - NANOCIRCUITRY, DEFECT TOLERANCE AND QUANTUM LOGIC

The geometrical scaling era of microelectronics technology will end ar ound the year 2010, if current extrapolations of physical and economic issues are valid. Computers built then should be 256 times as capable as the current generation, according to industry projections. However , physical laws suggest that it should be possible to compute non-reve rsibly at least 10(9) times present speeds with the expenditure of onl y 1W of electrical power. The challenges faced by those who intend to build affordable appliances with capabilities far beyond those of micr oelectronic circuits are to invent new computer architectures suitable for nanometre-scale devices and techniques to fabricate and assemble vast numbers of such devices inexpensively. These circuits will operat e according to quantum mechanical principles: and will necessarily be very different from those based on present technology.