HP Labs Breaches A Nanotech BarrierHP Labs Breaches A Nanotech Barrier

Hewlett-Packard scientists reported last week that they've found a way to potentially replace silicon transistors with electrically switchable molecules, knocking aside a big barrier in the quest to construct computers that harness the strange effects of quantum mechanics. HP has been assembling a portfolio of related technology for more than six years, and its latest breakthrough could yield more complex experiments aimed at replacing conventional microelectronics with a breed of quantum computers that could propel the industry through the coming decades.

In a paper published Feb. 1 in the Journal of Applied Physics, the researchers reported that they've built a molecular-scale "crossbar latch" that can flip a binary 0 to a 1 and vice versa and preserve the output of that computation for use in subsequent calculations. The switch, whose key component measures just a single layer of molecules thick, also can restore weakened electrical signals so the distinction between 0s and 1s stays crisp.

"This was the missing piece," says Stan Williams, an HP senior fellow and director of HP's quantum science research group. As silicon components reach the nanometer scale, measured in billionths of a meter, scientists foresee a time within the next decade or so when the effects of the quantum mechanical laws that govern the atomic realm make computing advantages hard to realize. For example, a quantum effect called "tunneling" can impair transistors by causing electrons to leak through their gates, throwing off the distinctions between 0s and 1s that computers rely on to perform their logic. HP's approach, on the other hand, exploits the tunneling effect. "We've turned these quantum mechanical effects into the way the device functions, rather than a barrier," Williams says.

HP has been researching what it calls "molecular electronics" since 1996 and holds about a dozen patents in the area. Its latest work, patented in 2003, was funded by the Defense Advanced Research Projects Agency. The molecular-scale crossbar latch consists of three crisscrossing platinum and titanium wires joined by a layer of electrically switchable molecules measuring 2.8 nanometers thick. Traditional computers use semiconductor materials to form the latch that preserves the output of a computation for later use. "We've designed a device that keeps working and works even better in the atomic scale," says Phil Kuekes, a senior computer architect at HP Labs.

James Ellenbogen, a senior principal scientist in the nanosystems group at Mitre Corp., a not-for-profit company that manages three federally funded research-and-development centers, says HP's advance eventually will give molecular electronics designers the ability to string nanoscale elements together to perform extended computations and move data around a system. It eliminates an obstacle to HP's plans to pursue a molecular-scale computer and could prove less expensive than traditional semiconductor fabrication techniques. "They've knocked down one of the things that was in the way of their strategy," Ellenbogen says, "and they've done a very clever and lovely piece of scientific work in the process."