Do your electronic gadgets have a speed limit?

As smartphones and tablets get faster, as the internet spreads satelliteslike 4G is progressing towards 5G (which is not yet fully in force despite what manufacturers and marketers want you to believe), is there such a thing as too fast for technology?

quantum physics says so. Researchers have now found the ultimate limit of speed and power that electronics cannot exceed – although the advantage is that these extreme limits are impossible to reach with current technology, so we will not miss anything. Process in semiconductors generate an electric current. The shorter the signal, the less time it takes for these processes to occur and the more instant gratification your gadgets provide. It seems like it could go on forever. Unfortunately, the speed potential is not infinite.

What slows down something like a computer chip is actually the speed of the energy transfer involved. Zapping a semiconductor with laser pulses accelerates the electrons in its atoms. The shorter the electric current, the faster the transfer of energy, until the electrons are pushed until this transfer cannot go any faster. Researchers Marcus Ossiander of Harvard University and Christoph Lemell of Vienna University of Technology, who led and co-authored a study recently published in Nature Communicationfigured out what that elusive upper limit was.

“To induce a current, you have to create an asymmetry in the movement of electrons,” Ossiander told SYFY WIRE. “To do this, you again want to apply an electric field, so most electrons prefer to follow the direction of this field. But they can’t always do what they want.

So what is the ultimate rate at which electricity can be transferred? Using lasers, which are much faster and more precise than regular transistors, the research team concluded that they could not go beyond the petahertz. It’s a million gigahertz or a-million billion hertz. So that you can understand exactly how fast it is, consider one hertz like a second. Now try to imagine a million billionth of that. Reaching it means you have to get electrons out of a semiconductor, which means you have to move them to different places. Electrons in solids must be moved artificially because their motions cancel each other out otherwise.

“Our signal was a short laser pulse through an isolator, driven by a second, longer laser pulse,” Lemell said. “We then compared the measured current with the known electric field of the pulse. To transform information from rapid changes in the external field into a measured signal, the solid must be able to transmit currents at very high frequencies.

Semiconductors fall somewhere between conductors like metals, which allow electric currents to flow freely, and insulators such as plastic, which block the passage of an electric current. There are three main energy bands in an atom. The valance band is where the outer electrons hang out and they are bound to the nucleus. When these are moved towards the conduction band, which ironically is closest to the nucleus, they detach from the nucleus and therefore release electrons. They only have to cross the forbidden zone to get there.

“One of the achievements of our current work is that we were able to create light pulses with very high photon energies, much larger than what people can usually use,” Ossiander said. “We call the energy of our light vacuum ultraviolet or extreme ultraviolet.”

push electrons through the forbidden energy gap usually requires some applied force. The energy in this region is the same as the energy difference between the valence and conduction bands. There is only one problem. Short laser pulses — like the extreme UV pulse the researchers created in their lab — have a range of frequencies. As a pulse is shortened, its spectrum widens. Although you can pinpoint exactly when the electron was hit with extra energy, you don’t really know how much or what kind of energy it picked up.

It is thanks to the conditions under which this experiment was carried out that such a high speed could even be reached. Ossiander, Lemell and their team used lithium fluoride as a semiconductor and also had hypersensitive equipment to detect what the electrons were doing at any given time. They were able to tell exactly when the electrons reached a state where an insulator suddenly switched to a conductor. This happened fastest at one petahertz. More speed would have caused problems in the signals they tried to transmit.

“It will still take some time to miniaturize the lasers and setups needed to achieve such extreme time scales in the millions of parallel switches required for a processor and at a size and cost that can make it into our living rooms,” they said. said the researchers.

For just one realization of this upper limit, the space needed was about the same size (and as expensive) as a one-bedroom apartment. Our need for speed will have to wait.

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