Australian scientists believe they have taken a key step towards building a silicon quantum computer – a device that could take quantum computing from hype to mainstream.

Silicon quantum computers marry quantum technology with the same element – silicon – used in existing computer chips, so can hopefully be easily mass-produced. Australia leads the world in the technology, which competes with at least eight other types of quantum computer.

Classic computers perform calculations using ones and zeros. Quantum computers use qubits, which are in a quantum state of both one and zero at the same time.CREDIT:TONY MELOV / UNSW

But despite a decade of hype and billions of dollars in investment, quantum computing in general remains a long way off fulfilling its full promise, experts admit. At this stage, there are few uses for such a computer and scientists remain a long way from building a device that could calculate serious equations.

The Australian-led study, published on the front cover of leading journal Nature in January, shows silicon quantum computers can now be operated with better than 99 per cent accuracy.

“This has long been understood as the next big step you needed to take,” says Professor Andrea Morello of the University of NSW, who led the work.

Being 99 per cent-plus accurate seems a small achievement for a computer, but it’s a big deal in quantum because it is considered the threshold at which you could scale quantum processors into an actual computer, he says.

Professor Andrea Morello from UNSW.CREDIT:KEARON DE CLOUET / UNSW

Sydney Quantum Academy chief executive Professor Peter Turner, who was not involved in the research, says it’s “a worthy milestone, for sure.”

Classic computers perform calculations using ones and zeros. Quantum computers use qubits, which are in a quantum state of both one and zero at the same time. But if a qubit is disturbed, it turns back to a zero or one. That extreme fragility impairs their accuracy. Worse, unless your computer is at least 99 per cent accurate, as you add more qubits, the computer becomes even more inaccurate.

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A second study from the team, published in Advanced Materials in December, shows the quantum chips can be built using “ion implantation”, the same technology used to make silicon chips inside computers and smartphones.

“This ensures that our quantum breakthrough is compatible with the broader semiconductor industry,” says Professor David Jamieson, who led that work at the University of Melbourne.

A long way to go

Scientists talk of scaling up quantum manufacturing. But current machines are still hand-built. And making one that can do useful things remains a long way off.