Quantum Experiment Reveals Speed Limit For Electronics

Now scientists know how fast electronics could theoretically become. While computers and smartphones are getting faster, there are many limitations to how fast they can be – this is due to the properties of the materials as well as the laws of physics themselves.

To investigate the latter, a team from TU Wien (Vienna), TU Graz and the Max Planck Institute for Quantum Optics has created a very special installation using lasers and non-conductive materials. This scenario, although not an architecture of modern electronics, gave scientists the opportunity to test quantum mechanics to its limit.

And there is a limit. According to a paper published in Nature Communications, controlled processes involving light and electronics in materials cannot exceed one petahertz. That’s about 1,000 trillion processes per second. Commercially available processors have a clock speed of about 4.5 GHz, so the limit exceeds 250,000 times.

“For a long time, such processes were considered instantaneous,” said co-author Professor Christoph Lemel of TU Wien. “Today, however, we have the necessary technology to study in detail the temporal evolution of these ultrafast processes.”

The constraint comes from one of the cornerstones of quantum mechanics: the uncertainty principle. Perhaps you know this: the more accurately you know the position of a particle, the less accurately you can predict its momentum, and vice versa. This can also be applied to energy and time. Therefore, for higher speeds you need shorter laser pulses, which means that the energy is not defined exactly.

And energy is the key. Free electrons are needed for electricity to flow, and the energy supplied to the system can separate electrons from atoms. So if there is uncertainty about the energy you are delivering, your system may not work as you expect beyond a certain threshold of short-term pulses.

“We can say exactly at what point in time the free charge carriers are created, but not in what energy state they are,” Lemel explained. “Solids have different bands of energy, and with short laser pulses, many of them inevitably inhabit free charge carriers at the same time.”

Although the petahertz is a good roundabout, the team believes it is unlikely that electronics will come close to it. There are other physical properties associated with specific materials and specific installation that need to be tested to understand the actual physical speed limit. But at least now there are approaches that can reach those limits.

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