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Nature 406, 1047-1054 (31 August 2000) | doi:10.1038/35023282

Open Innovation Challenges

review article Ultimate physical limits to computation

Seth Lloyd1

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Computers are physical systems: the laws of physics dictate what they can and cannot do. In particular, the speed with which a physical device can process information is limited by its energy and the amount of information that it can process is limited by the number of degrees of freedom it possesses. Here I explore the physical limits of computation as determined by the speed of light c, the quantum scale planck and the gravitational constant G. As an example, I put quantitative bounds to the computational power of an 'ultimate laptop' with a mass of one kilogram confined to a volume of one litre.

Over the past half century, the amount of information that computers are capable of processing and the rate at which they process it has doubled every 18 months, a phenomenon known as Moore's law. A variety of technologies — most recently, integrated circuits — have enabled this exponential increase in information processing power.