High-tech speed limit: Scientists figure out the fastest possible speed of computers

GRAZ, Austria — Computers get faster and faster every single year. So, is there an actual limit that technology can’t pass? A new study finds that it seems there is. Researchers from Germany and Austria have found the maximum possible speed of a signal transmission in microchips — one petahertz.

How fast is that you ask? Scientists say that’s the equivalent of one million gigahertz. That’s also roughly 100,000 times faster than current microchip transistors can go today. Moreover, researchers aren’t certain if human technology will ever be able to reach this incredible rate of speed.

Make it smaller to make it faster

Researchers say there’s two ways scientists can make computers faster. The first is by making computer components smaller. This literally cuts down the distance data transmission signals have to travel between point A and point B.

The furthest this process can go is shrinking components down to the size of an atom. In microelectronics, an electric circuit cannot be any smaller.

The second way is by speeding up the switching signals of the microchip transistors themselves. These objects either block or allow a current to flow in the microchip. In terms of computer speed, researchers say “fast” means the same as “high-frequency.”

“The faster you want to go, the more high frequency the electromagnetic signal has to be – and at some point we come into the range of the frequency of light, which can also be considered or used as an electromagnetic signal,” says lead author and head of the Institute of Experimental Physics at Graz University of Technology, Martin Schultze, in a media release.

The team adds that this often takes place in optoelectronics, where light excites electrons in a semiconductor, sending them from the valence band — the area where electrons typically reside — to the conduction band. When electrons reach this band, they have enough energy to move freely in that particular material. All of this movement also creates an electric current.

The level of energy coming from this process depends on the semiconductor material and it lies within the frequency range of infra-red light. That frequency will also align with the maximum possible speed these materials can reach.

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Is glass the answer?

To reach these super speeds, study authors believe glass or ceramics — which are dielectric materials — can overcome the limitations other materials face. They require much more energy to excite electrons in comparison to semiconductors. The extra energy allows for the use of higher-frequency lights — creating faster data transmission.

The problem with this is dielectric materials can’t conduct electricity without breaking, according to study first author Marcus Ossiander.

“For example, if you apply an electromagnetic field to glass so that it conducts electricity, this usually results in the glass breaking and leaving a hole,” the post-doctoral researcher at Harvard says.

To solve that, the team kept their switching frequency so short that the dielectric materials did not have the time to break under the strain of conducting electricity. Specifically, the team used an ultra-short laser pulse with a frequency in the extreme UV light range.

Scientists bombarded a lithium fluoride sample with the laser pulse. Researchers explain that lithium fluoride has the largest gap between its valence band and its conduction band. The short bursts excited the electrons in the lithium fluoride, sending them into an energetic state capable of conducting electricity.

From there, a second, slightly longer laser pulse guided the electrons in a specific direction, creating an electric current detectable by electrodes on both sides of the material.

Study authors explain that this process allowed them to measure how quickly the material reacted to ultra-short laser pulses. It also reveals how long this process takes to generate a signal and how long dielectric materials can withstand exposure to these signals.

“It follows that at about one petahertz there is an upper limit for controlled optoelectronic processes,” says Joachim Burgförder from the Institute for Theoretical Physics at TU Wien.

The study is published in Nature Communications.

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About the Author

Chris Melore

Chris Melore has been a writer, researcher, editor, and producer in the New York-area since 2006. He won a local Emmy award for his work in sports television in 2011.

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