By Liam Mannix
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
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, recently published on the front cover of leading journal Nature, 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. 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.
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.
IBM’s 127-qubit processor holds the title of world’s most powerful quantum computer. A useful machine will need “millions, or even billions of qubits”, says Professor Jamieson.
Professor Turner says different people give different forecasts on how long that might take. “Some say five years, some say 50. Some holdouts still say it’s impossible,” he says.
Quantum computers are not comparable to regular computers: they are not designed to play video games or browse the web. Instead, they are useful for extremely specific problems that are difficult or impossible for classic computers to solve – modelling chemistry and cracking widely used encryption, possibly including bitcoin.
Much is made of the ability to crack encryption, but this may just be a step in an arms race: companies are already working to develop quantum-proof encryption.
Quantum scientists argue you can’t design programs until you have the hardware.
“There are fewer than we’d like,” admits Professor Turner. “But it’s not our generation that’s going to discover all these quantum algorithms – it’s the kids in high school right now.”
Thanks to large investments in the early 2000s, Australia once led the world in quantum computing. It is still a key player, but “we are losing our relevance, there is no doubt about that”, says Dr Simon Devitt, managing director of the quantum technology consultancy, H-bar.
“Starting in 2014 we started seeing the rest of the world really ramping up their efforts. And Australia is sitting here twiddling its thumbs.”
Dr Devitt says several key quantum research centres, including the Centre of Excellence for Quantum Computation and Communication, are due to close within the next three years unless their funding is renewed.
“We have no idea if Canberra is going to go through with a full-fed initiative in quantum, which is what we really need if we’re going to continue to be relevant in this space.”
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