Scientists develop record cold refrigerator that could unlock full potential of quantum computers

Researchers have successfully developed a record cold refrigerator that could help quantum computers work better.

Qubits, the fundamental units of quantum computers, must be kept at temperatures close to absolute zero to function without errors.

A new cooling technology developed by researchers at Chalmers University of Technology in Sweden and the University of Maryland in the United States may bring us closer to realising the full potential of quantum computing.

The cooling systems used today, called dilution refrigerators, bring the qubits to about 50 millikelvins above absolute zero, according to the Chalmers University of Technology.

In an experiment, a new quantum refrigerator brought the qubits to 22 millikelvins, a factor 10,000 times colder than the room temperature, according to the research team.

The closer to absolute zero or zero Kelvin, which is equivalent to minus 273.15 degrees Celsius, the more reliable quantum computation can be.

But it also becomes harder to reach absolute zero as the temperature gets lower.

Fridge is 'fully autonomous'

"If you think of what temperature is physically, it's just about essential vibrations. And you can think of bringing an object that vibrates a lot down to a state in which it vibrates less and less until it stays as still as it can be according to the laws of quantum mechanics. And when it's completely still, this is what you would call absolute zero," Simone Gasparinetti, an associate professor at Chalmers University of Technology and lead author of the study, told Euronews Next.

The team managed to make these vibrations 10,000 times smaller, which they said was a "record low" for the particular moulds.

Unlike dilution refrigerator systems that require constant external control, this quantum refrigerator operates on its own once it is set up.

The refrigerator uses three qubits and operates based on a system where warm and cold environments interact in a specific way to remove heat from a target qubit, the part of the quantum computer that needs to be cooled.

"Energy from the thermal environment, channeled through one of the quantum refrigerator’s two qubits, pumps heat from the target qubit into the quantum refrigerator’s second qubit, which is cold," Nicole Yunger Halpern, an assistant professor of physics at the University of Maryland, said in a statement.

"That cold qubit is thermalised to a cold environment, into which the target qubit’s heat is ultimately dumped".

Gasparinetti added: "The refrigerator is fully autonomous, which means, essentially, it only requires coupling to a hot and cold source to function. This is something that is in contrast to other techniques that would require, for example, precisely timed pulses or other forms of control".

"So essentially, you switch it on, and the qubits get cold, and then you can switch it off and start your computation," he said.

Bringing thermodynamics from theory to practice

Quantum thermodynamics, which combines quantum physics and thermodynamics, is a field that has been largely theoretical so far, according to researchers.

"In the last 50 years, we have miniaturised lots of components, especially, but not all electrical components," Gasparinetti said.

"We really had the desire to build a quantum machine, a thermal machine, that was useful," he added.

Researchers say this refrigerator helps qubits work with far fewer errors and for longer periods in quantum computers.

The team managed to reduce the error rate of quantum computing by 20-fold from the error rate of 0.02 to 0.01. 

This may seem small, but researchers say it’s important to minimise errors to ensure reliable calculations in quantum computing.

More work needs to be done

Quantum computers have the potential to revolutionise fundamental technologies in various sectors of society, with applications in medicine, energy, encryption, AI, and logistics.

However, researchers say more work needs to be done so that quantum computers can solve problems.

"These machines have to get better at many things before they are useful. And we also have to get better at finding ways to use these resources that we have. We have still not fully understood how to harness quantum resources to make useful computations and solve useful problems," Gasparinetti said.

Gasparinetti also says there’s a widespread misconception that quantum computers will replace classical computers like our laptops.

It's a technology that will instead enhance the classical computers to solve very specific problems, such as those related to logistics or drug discovery, and we still need classical computers to operate a quantum computer, he said.

"Experiments like the one we did actually show that you can have more functionality very close to the quantum components, which I think is a trend that we will see more of in the future," Gasparinetti said.

Researchers hope more quantum autonomous machines can be developed.

"The next question is what other problems could be solved autonomously?"

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