“Quantum computing allows you to solve certain problems in minutes that would take conventional computers centuries, or even thousands of years,” says Professor Michelle Simmons from the University of New South Wales (UNSW Sydney).
Rather than performing sequential calculations one after the other like conventional computers, these futuristic machines will carry out calculations in parallel.
Australia is leading the international race to develop a viable quantum computer in silicon. This powerhouse status is thanks in large part to Simmons, who is the Director of the ARC Centre of Excellence for Quantum Computation and Communication Technology.
The Centre comprises close to 180 researchers across UNSW Sydney, the University of Melbourne, the Australian National University, Griffith University, the University of Sydney, UNSW Canberra at ADFA and the University of Queensland.
Around the world, research groups have explored various approaches to developing a quantum computer, some involving exotic materials. Simmons and her Centre have focused on just two ‘implementation’ strategies: developing an optical quantum computer, where information is encoded in photons of light, and developing a solid-state quantum computer using silicon as the base material.
The latter is where they have demonstrated international leadership with pathways to scale to practical systems: “We have been systematically building that capability in Australia for over a decade, giving us a competitive edge” she says.
“We’re leading the field in atomic precision devices and it will be very hard for people to catch us.”
Solving specific complex problems
Simmons’ team has a detailed plan to build a 10-qubit integrated circuit device within five years, and is aiming for a 100-qubit system within the decade beyond that.
If all goes to plan, she says, quantum computers will excel at searching colossal datasets, solving complex optimisation problems, and modelling things like financial markets or simulating biological molecules – quantum technologies will provide important new modelling abilities that will improve the quality and speed of drug development.
Simmons says quantum computers could help transport and delivery companies dramatically reduce fuel consumption, or improve the pattern-recognition software in self-driving cars, making them safer and faster. For everyday people, benefits could range from real-time analysis of traffic and weather, to a new era of personalised medicine.
Entering the quantum realm
The unique ability of quantum computers stems from how information is encoded.
In conventional computers, information is represented by classical bits: the zeroes and ones of binary code, determined by a transistor device being switched ‘off’ or ‘on’. In the atomic-scale devices Simmons is renowned for fabricating, information is written on the electron-spin or nuclear spin of individual phosphorus atoms precisely positioned in silicon known as quantum bits, or qubits.
By cooling the device to extremely low temperatures and putting it in a magnetic field, they can create the 2-level quantum system where the spin behaves as a tiny bar magnet and either aligns with the field representing a zero state or against the field representing a one state analogous to classical information.
But qubits have spooky properties and can exist in a superposition of these states at the same time. A consequence of this is that the amount of information doubles with each new qubit added to a system, giving rise to an exponential increase in its computational power.
Furthermore, qubits also exhibit a strange state known as quantum entanglement. Any operation carried out, says Simmons, will affect all the qubits and their coherent states simultaneously.
“This is what enables the power of massive parallel processing,” she says.
With 300 qubits, it is theoretically possible to store as much classical information (ones and zeroes) as there are atoms in the universe. A system this size if error corrected would be more powerful than the most powerful supercomputer with billions of classical bits.
The silicon story and its advantages
In 1998, a physicist named Bruce Kane outlined a hypothetical approach for building a quantum computer in silicon using phosphorus atoms at the qubits.
Simmons, then at Cambridge University in the UK, had “exquisite control” over her GaAs quantum devices but was unable to make the same device twice.
“I was genuinely frustrated,” she recalls. “Bruce’s proposal got rid of all the things we knew were causing problems... and reduced the problem to just phosphorus and silicon. I thought the concept was about the simplest way you could make a reproducible quantum device, and it was on the edge of what was technically feasible.”
As the material used in all modern-day computer chips, silicon offers several advantages: it’s easy to manufacture, can be purified to contain no other spins and its properties are well understood thanks to trillions of dollars of R&D investment.
Simmons decided it was the “best material in the world to build a scalable quantum computer” and never looked back.
Coming to Australia to be a scientific leader
In 1999, Simmons made an “easy decision” to come to Australia: “I felt the Australian culture was much more open and collaborative than the US or UK, and had many more opportunities for young people to find leadership roles early in their career.”
With funding and academic freedom to pursue “ambitious and high-risk” projects, Simmons has led a steady flow of scientific breakthroughs and technical achievements.
Her team developed the world’s first single atom transistor and the narrowest conducting wires in silicon; they have demonstrated the ability to read-out the spin states of individual electron spins on single phosphorus atoms with the highest precision, and more recently, earned the distinction of having the ‘lowest noise’ of any silicon device. Interference or ‘noise’ from the surrounding environment can wreak havoc with the ability of qubits to keep their state, so this is an important achievement, she says.
In late 2015, the Australian Government promised A$26 million to help the Centre translate its research. This was quickly followed up with A$10 million pledges from the Commonwealth Bank of Australia and telecommunications giant Telstra.
The combined A$46 million puts the Centre in a healthy position to maintain its international leadership. Even if another research group demonstrates a viable quantum computer first, Simmons believes her team’s qubits will be superior: “We are confident we can come along with a better system.”
Michelle Simmons at her lab opening addressing Prime Minister Malcolm Turnbull and other guests. Credit: CQC2T
Checkmate: the importance of a childhood chess match
When Simmons was eight years old, she defeated her father in her first game of chess. It was a turning point in her childhood: “I think the reason why it resonated with me is that he really didn’t anticipate that I’d be able to win.”
Simmons says it inspired her to always embrace challenges, to work obsessively hard at mastering whatever it was she undertook, and to defy the expectations of other people.
This attitude has paid off in her scientific career: she was made a Fellow of the American Academy of Arts and Sciences, which includes 250 Nobel Laureates; and won the 2015 CSIRO Eureka Prize for Leadership in Science.
After receiving the 2017 L’Oréal-UNESCO for Women in Science Award, Simmons said: “Trying to control nature at its very smallest scale is such an exciting and rewarding field to be in."
"This has been my passion for many years and has such tremendous potential. I am honoured by this recognition and hope it inspires others.”