Tech + Engineering


First Carbon Nanotube Computer Is Slow, But Promising

The quest for speedier computer chips is heading into an uncertain future.

For decades, we’ve grown accustomed to staggering increases in speeds—today’s smartphones, for example, have as much or more processing power than laptops just a few years old. And desktop machines today could have qualified as supercomputers not long ago.

But as the tiny traces and gates on silicon chips get smaller and smaller, they’ll begin to bump up against the limits of physics. Soon, the materials currently used in computer chips won’t be able to move electrons sufficiently faster.

A scanning electron microscope image of a portion of the carbon nanotube computer

So scientists have been searching for possible replacements. One promising material is carbon nanotubes, which are essentially single-atom-thick sheets of carbon rolled up into tubes. Like many allotropes of carbon, nanotubes have unusual properties. Theoretically, a computer made of carbon nanotube semiconductors would be blisteringly fast, extremely energy efficient, and far better at dissipating heat than silicon chips. Faster, cooler chips that require less battery power could hasten the proliferation of computing power into parts of our lives we never envisioned.

But a carbon nanotube computer has only been theorized—until now. Researchers were able to craft individual transistors from carbon nanotubes, but never an entire computer. Yesterday, though, researchers from Stanford University announced they built the first-ever carbon nanotube computer.

Katherine Bourzac, reporting for Technology Review:

The carbon nanotube processor is comparable in capabilities to the Intel 4004, that company’s first microprocessor, which was released in 1971, says Subhasish Mitra, an electrical engineer at Stanford and one of the project’s co-leaders. The computer, described today in the journal Nature, runs a simple software instruction set called MIPS. It can switch between multiple tasks (counting and sorting numbers) and keep track of them, and it can fetch data from and send it back to an external memory.

The computer’s simple instruction set pales in comparison to today’s processors, making it slower to perform some tasks than a silicon equivalent with a larger instruction set. But it’s every bit as capable. The 142-transistor computer is what’s known as Turing complete; it can perform any calculation thrown at it if given enough time. As Max Shulaker, a graduate student in the lab, told the New York Times, “We could in principle run 64-bit Windows, but it would take millions of years.”

Carbon nanotube computers are still a long ways from our laptops or smartphones, and some experts and companies—including Intel—doubt that the material is truly suitable for mass-market chips. But given the pace at which silicon chip features continue to shrink, we’ll either find an alternative be forced to contend with the limits physics imposes on them. Carbon nanotubes may be that alternative.