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It鈥檚 been said that quantum computing will be like going from candlelight to electric light in the way it will transform how we live. Quite a picture, but what exactly is quantum computing?

For the answer to that question, we鈥檒l have to visit a scale of existence so small that the usual rules of physics are warped, stretched and broken, and there are few layperson terms to lean on. Strap yourself in.

Luckily, we have a world-leading researcher in quantum computing, Professor David Reilly, to guide us. 鈥淢ost modern technologies are largely based on electromagnetism and Newtonian mechanics,鈥� says Reilly in a meeting room at the University鈥檚 Nano Hub. 鈥淨uantum computing taps into an enormous new area of nano physics that we haven鈥檛 harnessed yet.鈥�

With his youthful looks and laid-back demeanour, Reilly isn鈥檛 how you might picture a quantum physicist. He has five Fender guitars (with not much time to play them), and a weakness for single malt Scotches. That said, science has never been far below the surface. As a child, he would pull apart flashlights to see how they worked. During his PhD years, knowledge was more important than sleep; he often worked past 3am to finish experiments.

鈥淪ometimes you鈥檇 be the only person in the world with this new piece of knowledge. It鈥檚 a pretty wild feeling.鈥� A good place to start the quantum computing story is with the humble transistor, which is simply a switch that allows, blocks or varies the flow of electricity, or more correctly, electrons. Invented in 1947, it replaced the large, energy-hungry vacuum tubes in radios and amplifiers, also finding its way into computers.

This off/on gate effect of transistors is the origin of the zeroes and ones idea in traditional (aka classical) computers. Ever-shrinking transistors are also how computers have gone from room-filing monsters to tiny devices in our pockets 鈥� currently, just one square millimetre of computer chip can hold 100 million transistors.

Incredible, yes, but also unsustainable. With transistors now operating at the size of atoms, they literally can鈥檛 get much smaller, and they鈥檙e now at a scale where the different, nanoscale laws of physics are warping and compromising their usefulness. 鈥淎t that scale, an electron stops behaving like a ball being stopped by the transistor gate,鈥� Reilly says. 鈥淚t鈥檚 more like a wave. It can actually tunnel through or teleport to the other side, so the on/off effect is lost.鈥�

Quantum computing seeks to solve this problem, but it also promises a great leap forward. It鈥檚 based on the idea that transistors can be replaced by actual atomic particles where the zeros and ones aren鈥檛 predicated on the flow or non-flow of electrons, but on the property or energy state of the atomic particle itself.

These particles can come from various sources (and are usually engineered in nanoscale devices) but they鈥檙e called collectively, qubits. Now things get trickier. Yes, tricker. Where a transistor can be either one or zero, it鈥檚 a weird fact of quantum physics, that a qubit can be one or zero at the same time, like a spinning coin that holds the possibility of both heads and tails.

For a single qubit, this doubles the one-andzero mechanism. And for every qubit added, the one/zero combinations increase exponentially.

It is envisaged that quantum computers could have billions of qubits, representing phenomenal computing power. That鈥檚 very broadly the theory, but what currently keeps Reilly up at night is how to build the machinery that will allow the theory to impact the real world.

This machine would need a mechanism for manipulating the state of the qubits and a way of inputting and outputting information. As an added challenge, to make it all controllable, the machine would have to operate at minus 273掳C, just a shade above absolute zero. 鈥淗ow to do all that is technically and fundamentally challenging. There are big scientific questions, big engineering questions, but that鈥檚 what we do here,鈥� Reilly says, unflustered.

The quality of the work happening at the Hub was powerfully endorsed in 2017, when the Microsoft Corporation proposed a research partnership with the University, one of only four such arrangements Microsoft has in the world. 鈥淭his is not a research grant," Reilly says. 鈥淢icrosoft have been working in quantum computing since 2005 and they鈥檙e in it for the long haul. Now we鈥檙e working together, elbow to elbow in the labs, on something where every part is a work in progress.

It鈥檚 a partnership advancing a frontier.鈥� Reilly鈥檚 role sees him straddling the corporate and the academic, where deep knowledge is important but always with the goal of creating something real. Remembering how even great work can vanish into academic papers, Reilly says, 鈥淭he thought of not knowing whether this technology can come alive, I find to be scary. Connecting the discovery bit to the industry engineering machine means you actually see the whole system come together. That鈥檚 exciting.鈥�

So, where might quantum computing be put to work? The first thing to know is that our classical computers will not disappear from homes or offices. Quantum computers work on a scale well beyond emails, video games and spreadsheets. They will be about hugely accelerating global research and production.

鈥淚f you look at the top 10, classicaltype super computers on the planet right now, you鈥檒l find some are doing defence applications, like simulating weapons,鈥� Reilly says. 鈥淏ut a big chunk of them, are renting time out to pharmaceutical companies to understand the basic chemistry of different types of drugs which is really complex stuff.鈥�

These are the areas 鈥� industrial chemistry, pharmaceuticals, climate, city planning 鈥� where quantum computing could bring unimagined speed and accuracy, and the possibility of much more.

鈥淕o back to the invention of things like the transistor and you鈥檒l see that humankind鈥檚 ability to imagine what a new technology might do in the longer term is pretty poor. 鈥淟ikewise, this new physics promises new technology,鈥� says Reilly. 鈥淎nd chances are, it will be revolutionary.鈥�

Written by George Dodd. Photography by Louise M Cooper.