By Leah Crane

Credit: Luca Petit for QuTech

Quantum computing is heating up. For the first time, quantum computer chips have been operated at a temperature above -272C, or 1 kelvin. That may still seem frigid, but it is just warm enough to potentially enable a huge leap in the capabilities.

Quantum computers are made of quantum bits, or qubits, which can be made in several different ways. One that is receiving attention from some of the fields big players consists of electrons on a silicon chip.

These systems only function at extremely low temperatures below 100 millikelvin, or -273.05C so the qubits have to be stored in powerful refrigerators. The electronics that power them wont run at such low temperatures, and also emit heat that could disrupt the qubits, so they are generally stored outside the refrigerators with each qubit is connected by a wire to its electronic controller.

Eventually, for useful quantum computing, we will need to go to something like a million qubits, and this sort of brute force method, with one wire per qubit, wont work any more, says Menno Veldhorst at QuTech in the Netherlands. It works for two qubits, but not for a million.

Veldhorst and his colleagues, along with another team led by researchers at the University of New South Wales in Australia, have now demonstrated that these qubits can be operated at higher temperatures. The latter team showed they were able to control the state of two qubits on a chip at temperatures up to 1.5 kelvin, and Veldhorsts group used two qubits at 1.1 kelvin in what is called a logic gate, which performs the basic operations that make up more complex calculations.

Now that we know the qubits themselves can function at higher temperatures, the next step is incorporating the electronics onto the same chip. I hope that after we have that circuit, it wont be too hard to scale to something with practical applications, says Veldhorst.

Those quantum circuits will be similar in many ways to the circuits we use for traditional computers, so they can be scaled up relatively easily compared with other kinds of quantum computers, he says.

Journal references: Nature, DOI: 10.1038/s41586-020-2170-7 and DOI: 10.1038/s41586-020-2171-6

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Quantum computer chips demonstrated at the highest temperatures ever - New Scientist News