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Computers Have Speed Limit as ­nbreakable as Speed of Light, Say Physicists


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researcher in UCSB clean room

A researcher holds a mask that will be used in building a 4-qbit chip in the UCSB clean lab.

Credit: James Neeley / Flickr

Boston University physicists Lev Levitin and Tommaso Toffoli have demonstrated that if processors continue to improve in accordance with Moore's Law, an unbreakable speed barrier will be reached in approximately 75 years. Even with new technologies, there will still be an absolute ceiling for computing speed, no matter how small components get, according to Levitin and Toffoli.

The two physicists have created an equation for the minimum amount of time it takes for a single computation to occur, which establishes the speed limit for all possible computers. Using the equation, Levitin and Toffoli calculated that, for every unit of energy, a perfect quantum computer produces 10 quadrillion more operations each second than today's fastest processors. However, if following Moore's Law, it would take about 75 to 80 years to achieve this quantum limit, and no system can overcome that limit.

"It doesn’t depend on the physical nature of the system or how it's implemented, what algorithm you use for computation," Levitin says. "This bound poses an absolute law of nature, just like the speed of light." The physicists note that technological barriers may slow down Moore's Law as technology approaches the limit.

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