The last 25 years have witnessed astonishing advances in the fields of microelectronics and computation. The first integrated circuit microprocessor, the Intel 4004, was able to perform roughly 5000 binary-coded decimal additions per second with a total power consumption of about 10 W (~500 additions per joule) in 1971, whereas modern microprocessors can perform ~3 x [10.sup.6] additions per joule. The 1997 National Technology Roadmap for Semiconductors (1) calls for an additional factor of [10.sup.3] increase in the computational efficiency by the year 2012. If this goal is attained, then performance of the silicon-based integrated circuit will have improved by nearly seven orders of magnitude in 40 years, using energy consumed per operation as a metric, with a single manufacturing paradigm. Although complementary metal oxide semiconductor (CMOS) technology is predicted by many researchers to run into significant physical limitations shortly after 2010 (2), the energy cost of an addition operation will still be nowhere near any fundamental physical limit. A crude estimate of the energy required to add two 10-digit decimal numbers, based on a thermodynamic analysis of nonreversible Boolean logic steps (3, 4) is ~100*k*T*1n(2), which implies that 3 x [10.sup.18] additions per joule can be performed at room temperature without any reversible steps.…

March 30, 2013

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