Scientists calculate the absolute quantum speed limit for electronics


It often feels like electronics will keep getting faster forever, but at some point the laws of physics will kick in to put a stop to it. Scientists have now calculated the ultimate speed limit – the point at which quantum mechanics prevent microchips from going any faster.

It’s well known that nothing travels faster than light, and that’s true for electronics – systems that use light to control electricity, known as optoelectronics, are the fastest devices around. . And in the new study, researchers from TU Wien, TU Graz and the Max Planck Institute for Quantum Optics identified the upper limit of how fast optoelectronics could possibly reach.

The team conducted experiments using semiconductor materials and lasers. The semiconductor is struck by an ultra-short laser pulse, which shifts the material’s electrons to a higher energy state, allowing them to move freely. Then a second, slightly longer laser pulse sends them in a certain direction, producing an electric current.

A diagram illustrating how ultra-short laser pulses (blue) donate electrons into semiconductor energy, then a second laser pulse (red) sends them flying in certain directions to produce an electric current

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Using this technique, along with complex computer simulations, the team hit semiconductors with increasingly shorter laser pulses. But at some point the process starts to run into Heisenberg’s uncertainty principle – it’s the weird quantum quirk where the more precisely you measure one characteristic of a particle, the less sure you can be of another. .

In this case, the use of shorter laser pulses means that observers can tell exactly when the electrons are gaining energy, but this comes at the cost of less certainty about the amount of energy they gain. And that’s a major problem for electronic devices, because not knowing the exact energies of electrons means they can’t be controlled as precisely.

From this, the team calculated the absolute upper limit of how fast optoelectronic systems could possibly reach – one petahertz, or one million gigahertz. It’s a hard limit, which cannot be circumvented because the barrier is rooted in the very laws of quantum physics.

Of course, we’re unlikely to have to worry about it directly anyway. The team says other technological hurdles will arise long before optoelectronic devices reach the PHz domain. But understanding the hard limit could help develop better electronics.

The research was published in the journal Nature Communication.

Source: TU Vienna


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