Researchers Build a Working Carbon Nanotube Computer

“It’s a rudimentary demonstration that carbon nanotubes can be used to build a universal computer”

A group of Stanford researchers has moved a step closer to answering the question of what happens when silicon, the standard material in today’s microelectronic circuits, reaches its fundamental limits for use in increasingly small transistors.

In a paper in the journal Nature on Wednesday, the researchers reported that they had successfully built a working computer — albeit an extremely simple one — entirely from transistors fashioned from carbon nanotubes. The nanotubes, which are cylinder-shaped molecules, have long held the promise of allowing smaller, faster and lower-powered computing, though they have proved difficult to work with.

The Stanford Robust Systems Group, however, has made significant progress in the last 18 months, advancing from building individual carbon nanotube transistors to simple electronic circuits made by interconnecting the transistors, and this week to a complete computer made from an ensemble of just 142 low-power transistors.

While Stanford’s prototype computer is assembled from transistors that are gargantuan by industry standards — one micron vs. 22 nanometers — it is what computer scientists refer to as a “Turing complete” machine, meaning that it is capable of performing any computation, given enough time.

“It can run two programs concurrently, a counting program and a sorting program,” said H.S. Philip Wong, a Stanford University electrical engineer, and one of the leaders of the group. “We’ve spent a tremendous amount of time on this; in fact we’ve spent two generations of students on this.”

The computer is based on a subset of 20 of the instructions used by the commercial MIPS microprocessor, which itself was designed by a group of Stanford researchers led by Stanford’s current president, John Hennessy, during the 1980s.

“I think this is a really nice piece of work,” said Supratik Guha, director of physical sciences at I.B.M.’s Thomas J. Watson Research Center. “It’s a rudimentary demonstration that carbon nanotubes can be used to build a universal computer, or a Turing-complete machine. This is not the most efficient computer, but that wasn’t the point. It’s one of the first steps.”

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