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Australian breakthrough brings quantum computing closer

Supercomputers that can analyse major data sets will one day be superseded by quantum computing. AAP

Quantum computers that can solve complex problems in finance, health, security and defence are a step closer after a team of Australian and British researchers created the first working quantum bit based on a single atom in silicon.

In a paper published today in Nature, researchers from UNSW, the University of Melbourne and London’s University College write that a single atom is the prototypical quantum system, and a natural candidate for a quantum bit, or qubit - the elementary unit of a quantum computer.

“This work is a major step forward in developing quantum computers based on single electrons,” said Peter Rohde, postdoctoral research fellow in quantum computation at Macquarie University

Dr Rohde said quantum computing allows information to be encoded and processed according to the laws of quantum mechanics, giving quantum computers power well beyond what classical computers are capable of.

That power is expected to have applications in three key areas: searching large databases, cracking modern encryption, and modelling atomic systems, such as biological molecules and drugs.

The research team, led by UNSW’s Andrea Morello and Andrew Dzurak, have described how they were able to use the “spin”, or magnetic orientation of an electron bound to a single atom embedded in a silicon chip to read and write information.

“This is a remarkable scientific achievement – governing nature at its most fundamental level – and has profound implications for quantum computing,” Professor Dzurak said.

There are many proposed implementations for how to build a quantum computer, using different types of quantum systems to encode qubits, Dr Rohde said.

“The open question is how scalable this approach is - that is, how easy is it to expand this type of system to have many qubits, which is what would be required to build a large-scale quantum computer.”

One of the big questions in quantum computing is what ultimate system will be used said Thomas Stace, senior lecturer in physics, quantum information at University of Queensland.

“There’s experiments in all sorts of systems, ranging from photons to superconducting electronic devices.”

Dr Stace said the advantage of silicon is that it’s a well-understood material, with an entire computing industry built around it.

But in order for quantum computing to do something useful that is not able to be done by a classical computer, Dr Stace said far more qubits would be required.

“To do useful things like factoring numbers or simulating chemistry you probably need several hundred logical qubits.”

The research team said its next goal is to combine pairs of qubits to create a two-qubit logic state, which is the basic processing unit of a quantum computer.

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