Australian scientists closer to building silicon-based quantum computer

A group of Australian scientists are close to implementing the basic building blocks required to create a quantum computer, but by using silicon rather than atoms electromagnetically suspended in a vacuum.

Researchers at the University of New South Wales (UNSW) are almost at the point of perfecting their technique of implementing quantum bits — or qubits — in silicon atoms.

Qubits form the building blocks for quantum computers of the future, storing information in quantum states, the equivalent of our current digital 1s and 0s. In order to be of any use, however, the qubits need to have a high degree of accuracy, with researchers being able to retrieve values that they might "write" using a qubit.

At the moment, the benchmark for the perfect qubit is one that uses "Ion Trap" technology — a single atom that has been isolated within an electromagnetic trap inside a vacuum chamber. The significance of this technology won its researchers Serge Haroche and David J Wineland the 2012 Nobel Prize in Physics.

The research carried out by UNSW scientists, however, takes this potentially a step closer by implementing a qubit using the nucleus of a single silicon atom — about one millionth the size of the whole atom. This should, theoretically, make it much simpler to connect to existing silicon-based technology.

"Our nuclear spin qubit operates at a similar level of accuracy [as Ion Trap technology], but it's not in a vacuum chamber — it's in a silicon chip that can be wired up and operated electrically like normal integrated circuits," associate professor Andrea Morello from UNSW's School of Electrical Engineering and Telecommunications said in a statement.

"Silicon is the dominant material in the microelectronics industry, which means our qubit is more compatible with existing industry technology and is more easily scalable."

Choosing to use the nucleus of the atom brings its own challenges, such as making it harder to measure, according to Morello's PhD student Jarryd Pla, but it also significantly reduces any interference from the "outside world".

"Our nuclear spin qubit can store information for longer times and with greater accuracy. This will greatly enhance our ability to carry out complex quantum calculations once we put many of these qubits together," Pla said.

Combining qubits is one of the next focuses for the research group. By using more of the basic building blocks together, researchers should be able to form logic gates, the equivalent of basic AND, OR, XOR, and NOT transistors used in computing to form complex integrated circuits.

If the research results in a functional quantum computer being built, such applications could include significant benefits to finance and healthcare industries as database searches, financial simulations, and the atomic modelling of biological systems becomes near instantaneous. On the other hand, it would also make it trivial to crack most forms of modern encryption.