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 -272°C, or 1 Kelvin. That may still seem frigid, but is just warm enough to potentially enable a huge leap in the capabilities of this kind of quantum computer.
Quantum computers are made of quantum bits, or qubits, which can be made in several different ways. One that’s receiving attention from some of the field’s big players consists of electrons on a silicon chip.
These systems only function at extremely low temperatures – below 100 millikelvin, or -273.05°C – so the qubits have to be stored in powerful refrigerators. The electronics that power them won’t 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 connected by a wire to its electronic controller.
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“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, won’t work anymore,” 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 from the University of New South Wales in Australia, 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 Veldhorst’s group used two qubits at 1.1 Kelvin in what’s 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 won’t 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 to 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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