'Cedric' is only a basic prototype but could be developed into a machine which is smaller, faster and more efficient than today's silicon models. Nanotubes have long been touted as the heir to silicon's throne, but building a working computer has proven awkward.
"In human terms, Cedric can count on his hands and sort the alphabet. But he is, in the full sense of the word, a computer," Max Shulaker.
Carbon nanotubes (CNTs) are hollow cylinders composed of a single sheet of carbon atoms. They have exceptional properties which make them ideal as a semiconductor material for building transistors, the on-off switches at the heart of electronics.
While single-nanotube transistors have been around for 15 years, no-one had ever put the jigsaw pieces together to make a useful computing device. CNTs do not grow in neat, parallel lines. The Stanford team built chips with CNTs which are 99.5% aligned - and designed a clever algorithm to bypass the remaining 0.5% which are askew.
They also eliminated a second type of imperfection - "metallic" CNTs - a small fraction of which always conduct electricity, instead of acting like semiconductors that can be switched off. To expunge these rogue elements, the team switched off all the "good" CNTs, then pumped the remaining "bad" ones full of electricity - until they vaporised. The result is a functioning circuit.
The Stanford team call their two-pronged technique "imperfection-immune design". Its greatest trick? You don't even have to know where the imperfections lie - you just "zap" the whole thing.
Shrinking the transistors is the next challenge for the Stanford team. At a width of eight microns (8,000 nanometres) they are much fatter than today's most advanced silicon chips.
Image by Norbert Von Der Groeben
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