UNSW Team Reports Breakthrough in Quantum Computing

A team of scientists from the University of New South Wales (UNSW) in Australia has measured for the first time accuracy of two-qubit operations in silicon - a feat that would enable companies build a full-scale quantum processor.

Computers today process information in binary bits that take either a 0 or 1 value while quantum computers depend on the related but superior concept of the qubit.

What makes qubits superior to conventional bits is that in addition to just occupying a 0 or 1 position, they can occupy both at the same time - what's known in quantum mechanics as the superposition.

"All quantum computations can be made up of one-qubit operations and two-qubit operations – they're the central building blocks of quantum computing," nanoelectronics researcher Andrew Dzurak from UNSW said in a statement.

The research, published in the prestigious journal Nature, promises quantum computers that would enable a vastly more powerful and faster way of making calculations than the computing power we've had till date.

In 2015, Dzurak and fellow researchers built the world's first quantum logic gate in silicon, so that two qubits could communicate with one another.

The experiments were performed by Wister Huang, a final-year PhD student in Electrical Engineering, and Dr Henry Yang, a senior research fellow at UNSW.

A number of groups around the world have since demonstrated two-qubit gates in silicon but the true accuracy of such a two-qubit gate was unknown.

"Fidelity is a critical parameter which determines how viable a qubit technology is – you can only tap into the tremendous power of quantum computing if the qubit operations are near perfect, with only tiny errors allowed," informed Dr Yang.

In this study, the team implemented and performed Clifford-based fidelity benchmarking -- a technique that can assess qubit accuracy across all technology platforms -- demonstrating an average two-qubit gate fidelity of 98 per cent.

Quantum computers will have a wide range of important applications in the future thanks to their ability to perform far more complex calculations at much greater speeds, including solving problems that are simply beyond the ability of today's computers.

"But for most of those important applications, millions of qubits will be needed, and you're going to have to correct quantum errors, even when they're small," said Professor Dzurak.

The researchers said that silicon as a technology platform is ideal for scaling up to the large numbers of qubits needed for universal quantum computing.

In another paper -- published in the Nature Electronics journal -- the same team achieved the record for the world's most accurate 1-qubit gate in a silicon quantum dot, with a remarkable fidelity of 99.96 per cent.