Sydney Uni predicts the unpredictable in quantum computing advancement

Scientists at the University of Sydney have developed a machine learning technique to predict the demise of quantum computing systems in a bid to keep quantum bits (qubits) from breaking.

According to the university, a significant obstacle in building reliable quantum technologies has been the randomisation of quantum systems by their environments -- known as decoherence -- which effectively destroys the useful quantum character.

Professor Biercuk from the University of Sydney's School of Physics and a chief investigator at the Australian Research Council's Centre of Excellence for Engineered Quantum Systems, said his group had demonstrated it was possible to suppress decoherence in a preventive manner, with the team developing a technique that uses machine learning to predict how the system would disintegrate.

"Much the way the individual components in mobile phones will eventually fail, so too do quantum systems," Biercuk said. "But in quantum technology the lifetime is generally measured in fractions of a second, rather than years."

Biercuk likened the quantum advancement to returning a serve in a game of tennis, noting that a player predicts where the ball will end up based on observations of the airborne ball. He said it is often known where the ball will land as the rules that govern how the ball will move, such as gravity, are regular and known, but if the rules randomly changed while the ball was in the air, it would be next to impossible to predict the future behaviour of that ball.

"And yet this situation is exactly what we had to deal with because the disintegration of quantum systems is random. Moreover, in the quantum realm observation erases quantumness, so our team needed to be able to guess how and when the system would randomly break," Biercuk said.

"We effectively needed to swing at the randomly moving tennis ball while blindfolded."

The university said the team's predictions were remarkably accurate, allowing them to use guesses pre-emptively to compensate for the anticipated changes. It also said that doing this in real time allowed the team to prevent the disintegration of the quantum character, and extended the useful lifetime of the qubits.

The university was awarded a slice of a multimillion dollar research grant from the United States Office of the Director of National Intelligence to advance its research in quantum computing last May.

At the time, it was said the undisclosed funding chunk would be injected into the Quantum Control Laboratory, which is led out of the university's AU$150 million Sydney Nanoscience Hub.

A team of researchers out of the University of New South Wales (UNSW), led by professor Michelle Simmons, is currently racing to build the world's first quantum computer in silicon.

Well on their way to achieving their goal, UNSW's engineers already unlocked the key to enabling quantum computer coding in silicon, announcing in late 2015 the team had the capability to write and manipulate a quantum version of computer code using two qubits in a silicon microchip.

According to UNSW, in achieving this breakthrough the team has removed lingering doubts that such operations can be made reliably enough to allow powerful quantum computers to become a reality.

The breakthrough followed on from an announcement made a month prior when another team of engineers from the university built a quantum logic gate in silicon, which made calculations between two qubits of information possible.

Engineers at UNSW then announced recently they had created a new qubit which remains in a stable superposition for 10 times longer than previously achieved, expanding the time during which calculations could be performed in a future silicon quantum computer.

Physicists at the Australian National University successfully completed an experiment to stop light in September, a critical step in developing future quantum computers, and in December the University of Technology launched its new Centre for Quantum Software and Information, dedicated to the development of the software and information processing infrastructure required to run applications at quantum scale.