Artist’s impression of a phosphorus atom (red sphere surrounded by a blue electron cloud, with spin) coupled to a silicon single-electron transistor, to achieve single-shot readout of the phosphorus electron spin. ((William Algar-Chuklin, College of Fine Arts, UNSW))

An Australian-led team of scientists has taken a big step forward in the race to develop a quantum computer.

Quantum computing relies on harnessing the laws of quantum physics — laws that apply to particles smaller than an atom — to get a computer to carry out many calculations at the same time.

Previous researchers have focused on using light, or materials other than silicon, in their work on quantum computers.

But the team led by engineers from the University of New South Wales and the University of Melbourne has been examining the properties of electrons embedded in silicon, which is cheaper and better understood and forms the basis of most electronics today.

To build a quantum computer, researchers need to be able to write information to an electron, by changing its "spin state," and to read information, by measuring its spin.

In an article published Monday in the journal Nature, the researchers said they have cracked the second part of this puzzle by creating a device that measures the spin state of a single electron in a single phosphorus atom inside a block of silicon.

"What we have demonstrated in this Nature paper is the ability to read out when the electron is in some random state," said Andrea Morello, co-leader of the project.

"The next thing is to prepare it in exactly the state we want it."

'Outstanding result'

Co-author Andrew Dzurak said that after a decade of work it is a special moment.


A team led by Andrew Dzurak, left, and Andrea Morello created a device that measures the spin state of a single electron in a single phosphorus atom inside a block of silicon. Next, they hope to prepare the electron in the state they want. ((University of New South Wales) )

"Quantum computers won't speed up all day-to-day computing," said Dzurak, a professor in the School of Electrical Engineering and Telecommunications at the University of New South Wales.

"But there are three areas where we know it will be much faster: cracking most modern forms of encryption; searching databases; and modelling atomic systems such as biological molecules and drugs."

Andrew White, a professor of the University of Queensland, who was not part of the research, said it is an "outstanding result."

"The whole world is exploring technologies to build quantum computers," he said. "The team have made the key advance of showing they can read out information from these spins in a single fast measurement that faithfully transmits the information.

"This opens up the road for silicon quantum computing."