Silicon is so important for electronics and computing that it’s become synonymous with technology – even getting a valley named after it – but the stuff still has its flaws. Now, scientists have created a way to make super-pure silicon chips that could pave the way for more stable quantum computers.
Silicon is favored for electronics for a few reasons. For one, it’s a semiconductor, meaning it can be made to conduct electricity to different levels under different conditions. Better yet, as the second most abundant element in Earth’s crust, it’s not hard to get hold of.
That’s worked well for decades, fueling the incredible expanse of computers, but for more advanced systems silicon’s purity becomes a limiting factor. Quantum computers can tap into the spooky realm of quantum physics to do stuff that regular computers can’t, but the quantum bits (qubits) that process and store information can lose their “coherence” at the slightest interference, like a tiny temperature fluctuation – or a silicon impurity.
“The problem is that while naturally occurring silicon is mostly the desirable isotope silicon-28, there’s also about 4.5% silicon-29,” said Professor David Jamieson, co-supervisor of the project. “Silicon-29 has an extra neutron in each atom’s nucleus that acts like a tiny rogue magnet, destroying quantum coherence and creating computing errors.”
So for the new study, researchers at the University of Melbourne and the University of Manchester developed a way to make silicon that’s far more pure. The team used a machine called an ion implanter to fire a beam of silicon-28 at a computer chip, which gradually replaces the silicon-29 impurities in the chip with the more desirable silicon-28. The end result was that the silicon-29 content was reduced from 4.5% down to just 0.0002%, or two parts per million.
“The great news is to purify silicon to this level, we can now use a standard machine – an ion implanter – that you would find in any semiconductor fabrication lab, tuned to a specific configuration that we designed,” said Professor Jamieson.
The more qubits a quantum computer has, the more powerful it can be – but also, the more vulnerable it is to errors. These new, super-pure silicon chips should help quantum computers with many qubits stay stable for longer, and the team says the next step is to test that out.
The research was published in the journal Nature Communications Materials.
Source: University of Melbourne