By Michael Irving
May 11, 2022
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Synchronized pairs of laser pulses drive the fastest logic
gates ever made, which could eventually give computers a million-fold speed
boost Photo credit: University of Rochester illustration / Michael Osadciw
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Logic gates take two inputs, compare them, and then output
a signal based on the result. They can, for example, output a 1 if both
incoming signals are a 1 or a 0, or if either or neither of them is a 1, among
other “rules.” Billions of individual logic gates are crammed into chips to
create processors, memory and other electronic components.
Logic gates don’t work instantaneously though – there’s a delay
on the order of nanoseconds as they process the inputs. That’s plenty fast
enough for modern computers, but there’s always room for improvement. And now
the Rochester team’s new logic gates blow them out of the water, processing
information in mere femtoseconds, which are a million times shorter than
nanoseconds.
To reach these extreme speeds, the team made junctions
consisting of a graphene wire connecting two gold electrodes. When the graphene
was zapped with synchronized pairs of laser pulses, electrons in the material
were excited, sending them zipping off towards one of the electrodes,
generating an electrical current.
By adjusting the phase of the laser pulses, the team was
able to generate a burst of one of two types of charge carriers, which would
either add up or cancel each other out – the former can be considered a 1
output and the latter a 0. The end result is an ultrafast logic gate, marking
the first proof of concept of an as-yet theoretical field known as lightwave
electronics.
“It will probably be a very long time before this technique
can be used in a computer chip, but at least we now know that lightwave
electronics is practically possible,” said Tobias Boolakee, lead researcher on
the study.
If these kinds of lightwave electronic devices ever do make
it to market, they could be millions of times faster than today’s computers.
Currently we measure processing speeds in Gigahertz (GHz), but these new logic
gates function on the scale of Petahertz (PHz). Previous studies have set that
as the absolute quantum limit of how fast light-based
computer systems could possibly get.
The research was published in the journal Nature.
Source: University of Rochester