Quantum Computing Milestone: Researchers Compute With ‘Hot’ Silicon Qubits

Two research groups say they’ve independently built quantum devices that can operate at temperatures above 1 Kelvin—15 times hotter than rival technologies can withstand.

The ability to work at higher temperatures is key to scaling up to the many qubits thought to be required for future commercial-grade quantum computers.

A team led by Andrew Dzurak and Henry Yang from the University of New South Wales in Australia performed a single-qubit operation on a quantum processor at 1.5 Kelvin. Separately, a team led by Menno Veldhorst of Delft University of Technology performed a two-qubit operation at 1.1 Kelvin. Jim Clarke, director of quantum hardware at Intel, is a co-author on the Delft paper. Both groups published descriptions of their devices today in Nature.

HongWen Jiang, a physicist at UCLA and a peer reviewer for both papers, described the research as “a technological breakthrough for semiconductor based quantum computing.”

In today’s quantum computers, qubits must be kept inside large dilution refrigerators at temperatures hovering just above absolute zero. Electronics required to manipulate and read the qubits produce too much heat and so remain outside of the fridge, which adds complexity (and many wires) to the system.

At the higher temperatures described in the new research, control electronics could be placed right next to the qubits on the same chip. Instead of requiring dilution refrigerators that use isotopes helium-3 and helium-4, the system could be cooled using only helium-4. That should reduce the costs of building quantum systems—Dzurak describes the potential difference as going from a few million US dollars to a few thousand.

The devices reported in Nature compute using silicon spin qubits. These qubits are particularly appealing to semiconductor makers such as Intel because devices based on them could be produced using modern semiconductor manufacturing techniques.

“To me, these works do represent, in rapid succession, pretty big milestones in silicon spin qubits,” says John Gamble, a peer reviewer for one of the papers and a senior quantum engineer at Microsoft. “It’s compelling work.”

Each silicon spin qubit consists of a few electrons held within a quantum dot. These quantum dots (which are different from the sort used in displays and cameras) are tiny wells or divots in silicon that lay just beneath the gate electrode of a conventional transistor. As charge flows through the transistor, electrons drop into the well, and electrostatic forces hold them in place.  [READ MORE]