Finns chill out quantum computers with qubit refrigerator to cut out errors

Refrigeration discovery could help pave way for viable quantum computers.
Written by Eeva Haaramo, Contributor

This one centimeter-sized silicon chip can help to cool down quantum bits.

Image: Kuan Yen Tan/Aalto University

Quantum computing is a revolutionary technology, but the obstacles to creating viable quantum computers remain significant.

Chipping away at the task is a team of Finnish researchers, who have found a way to cool down quantum bits, or qubits, using a quantum-circuit refrigerator.

"To my understanding, no one else has done a standalone component that can refrigerate a quantum system," Mikko Möttönen, quantum physicist and research team leader at Aalto University, tells ZDNet.

The significance of this development comes down to the fickle nature of qubits. Unlike in traditional computing, where electronic bits are set to a value of zero or one, qubits can simultaneously hold values of zero, one, or both. Consequently, they can carry out more computations in parallel and solve complex big-data problems much faster than today's systems.

But qubits are very sensitive to external perturbations and need to be well isolated, and that isolation can in turn cause them to heat up and result in calculation errors.

Furthermore, every qubit needs to be reset to its low-temperature ground state at the beginning of a computation. If qubits get too hot, they keep switching between different states.

This is where the cooling mechanism of the Finnish research team comes in. Their system works by tunneling single electrons through a 2nm-thick insulator.

By giving the electrons slightly less energy than that required for tunneling, they instead capture the missing energy from the nearby quantum device, which in turn loses energy and cools down.

This approach means most electrical quantum devices, including computers, could be initialised quickly and made more reliable.

So far, the system has been tested by postdoctoral researcher Kuan Yan Tan with qubit-like superconducting resonators, with the results published in scientific journal Nature Communications.

"In the experiments we did with the resonator, the temperature of the resonator we achieved was too high for quantum computer operations. So we have to show we can cool down to even lower temperatures," Möttönen explains.

In addition to this goal, the next steps for the team will be to test the system with actual quantum bits and make its on-off switch faster.

Möttönen estimates that viable practical applications could be possible in a few years' time, but says it is too early to speculate when these applications could turn into commercial products.

Möttönen's team is only one of the many companies and research organisations working on quantum computing, including tech giants Google, IBM and Microsoft. Despite all these efforts, Möttönen remains cautious when pressed about when the world will finally see the first commercial quantum computer.

"It's almost impossible at this stage to say when. But what I can say is it's more likely we will get there at some point than that we don't," Möttönen says.

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