HP’s ‘Crossbar Latch’ to Replace Transistors?

Researchers at HP have come up with a new signal
technology they claim could replace transistors in computers one day.

In a paper published in Tuesday’s Journal of Applied Physics, three
members of HP Labs’ Quantum Science Research (QSR) group demonstrated
what they call a “crossbar latch.”

A latch consists of a single wire
acting as a signal line, crossed by two control lines with an
electrically switchable nanoscale junction where they intersect. The
technology is so small, HP claims thousands of the strands could fit
across the diameter of a human hair.

“We are re-inventing the computer at the molecular scale,” Stan
Williams, HP senior fellow, QSR director and one of the authors of the
paper, said in a statement. “The crossbar latch provides a key element
needed for building a computer using nanometer-sized devices that are
relatively inexpensive and easy to build.”

Similar to the way that silicon-based transistors perform in
computers today, the researchers said the crossbar latches use a
sequence of voltage impulses to the control lines and using switches
arranged in opposite polarities.

The result is that the crossbar latches can perform the three basic
operations that comprise the primary logic of a circuit and are essential
for basic computer functions. In addition, the researchers said the new
latch technology could also restore a circuit to its ideal voltage. That
would let designers chain many simple gates together, allowing them to
perform computations.

Researchers are not ready to discard the current transistor
technology just yet. While current silicon transistor
technology can also perform the same operations and restore signals, the
researchers generally believe that transistors will not be able to
shrink down to the size of a few nanometers and remain operable.

“Transistors will continue to be used for years to come with
conventional silicon circuits,” Phil Kuekes, senior computer architect
with HP’s QSR and another one of the paper’s authors, said in a
statement. “But this could someday replace transistors in computers,
just as transistors replaced vacuum tubes and vacuum tubes replaced
electromagnetic relays before them.”

Kuekes was previously awarded a patent on the crossbar latch (U.S.
6,586,965) in July 2003. Duncan Stewart, a QSR scientist and the third
author, performed most of the testing that demonstrated that the device
actually works.

“We have previously demonstrated that we could make a working memory
with molecular-scale junctions and logic devices that could perform
simple logic operations,” Stewart said. “With the crossbar latch, we now
have the final component theoretically needed for performing the
multiple processing steps required for useful computing at the

HP said its researchers are also looking at how to use the latches in
tiny devices so manufacturers can produce them cheaper and in mass

The research on the crossbar latch was partially supported by the
Defense Advanced Research Projects Agency.

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