Australians set new quantum computing accuracy benchmarks

Our old friend Andrea Morello has chalked up another milestone in his groundbreaking work on quantum computing, setting new standards of accuracy.

His team is one of two in Australia working in the same laboratories at the University of New South Wales to find solutions to provide accuracy above 99% in quantum computing – the critical challenge that has held back the development of powerful quantum computers.

Both findings were published simultaneously in the journal Nature Nanotechnology and the two teams joined forced to explain the significance of their work in the video above.

The teams used different approaches to make the super-accurate quantum bits, or "qubits" – the building blocks for quantum computers.

"For quantum computing to become a reality we need to operate the bits with very low error rates," says Scientia Professor Andrew Dzurak, who is Director of the Australian National Fabrication Facility at UNSW, where the devices were made.

"We've now come up with two parallel pathways for building a quantum computer in silicon, each of which shows this super accuracy," says Morello from UNSW's School of Electrical Engineering and Telecommunications.

Dzurak's team discovered a way to create an "artificial atom" qubit with a device similar to a silicon transistor. Menno Veldhorst, lead author on the paper reporting the artificial atom qubit, says, "It is really amazing that we can make such an accurate qubit using pretty much the same devices as we have in our laptops and phones".

Morello's team, by contrast, is continuing its work with the "natural" phosphorus atom qubit. Dr Juha Muhonen, a post-doctoral researcher and lead author on the natural atom qubit paper, notes: "The phosphorus atom contains in fact two qubits: the electron, and the nucleus. With the nucleus in particular, we have achieved accuracy close to 99.99%. That means only one error for every 10,000 quantum operations."

Both approaches have one thing in common, though. Both natural and artificial atom qubits are placed inside a thin layer of specially purified silicon, containing only the silicon-28 isotope. This isotope is perfectly non-magnetic and, unlike those in naturally occurring silicon, does not disturb the quantum bit. The purified silicon was provided through collaboration with Professor Kohei Itoh from Keio University in Japan.

The next step, now, is to try and build pairs of highly accurate quantum bits. Large quantum computers are expected to consist of many thousands or millions of qubits and may integrate both natural and artificial atoms.

"For our two groups to simultaneously obtain these dramatic results with two quite different systems is very special, in particular because we are really great mates," adds Dzurak.

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