Germanium superconductor could help build reliable quantum computers

A superconductor made from germanium, a material commonly used to build computer chips, could one day create better and more reliable quantum computers.

Superconductors are materials which conduct electricity with no resistance, which is useful if you’re making any sort of electrical device. They also maintain quantum coherence, which is beneficial if you’re trying to build a useful quantum computer.

But while previous superconductors have tended to be unusual materials which would not be easy to incorporate into computer chips, Peter Jacobson at the University of Queensland and his colleagues have created one from germanium, which is already widely used by the computing industry.

The researchers created their superconductor by infusing a film of germanium with gallium, in a process known as doping. Previous research along these lines found that the combination eventually became unstable, but to get around the team used x-rays to force more gallium into the material and create uniform and stable patterns.

Like other known superconductors, however, this new material does not work at room temperature. It needs to be cooled to 3.5 Kelvin, which is approximately -270°C.

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David Cardwell at the University of Cambridge says that need for extremely cold temperatures rules it out for use in consumer devices, but that it could be a perfect fit for quantum computing because they also tend to need super-cooling.

“It could be transformational for quantum,” says Cardwell. “This gives a whole new level of functionality, because you’ve got a very cold environment anyway. That would be, I think, the obvious starting point.”

Jacobson says that previous work that layered superconductors on top of semiconductors, a key component of computing devices, caused defects in the crystal structure, which cause problems when it comes to application. “Disorder is really a parasitic effect in quantum technology,” he says. “It causes absorption of your signals.”

But the new material allows layers of gallium-doped germanium and layers of silicon to sit on top of each other with a uniform crystal structure throughout, potentially allowing for manufacture of chips that merge the best properties of semiconductors and superconductors.