A drastic reduction in hardware overhead for quantum computing with new error correcting techniques

A scientist at the University of Sydney has achieved what one quantum industry insider has described as “something that many researchers thought was impossible”.

Dr. Benjamin Brown from the School of Physics has developed a type of error-correcting code for quantum computers that will free up more hardware to do useful calculations. It also provides an approach that will allow companies like Google and IBM to design better quantum microchips.

He did this by applying already known code that operates in three-dimensions to a two-dimensional framework.

“The trick is to use time as the third dimension. I’m using two physical dimensions and adding in time as the third dimension,” Dr. Brown said. “This opens up possibilities we didn’t have before.”

His research is published today in Science Advances.

“It’s a bit like knitting,” he said. “Each row is like a one-dimensional line. You knit row after row of wool and, over time, this produces a two-dimensional panel of material.”

Fault-tolerant quantum computers

Reducing errors in quantum computing is one of the biggest challenges facing scientists before they can build machines large enough to solve useful problems.

“Because quantum information is so fragile, it produces a lot of errors,” said Dr. Brown, a research fellow at the University of Sydney Nano Institute.

Completely eradicating these errors is impossible, so the goal is to develop a “fault-tolerant” architecture where useful processing operations far outweigh error-correcting operations.

“Your mobile phone or laptop will perform billions of operations over many years before a single error triggers a blank screen or some other malfunction. Current quantum operations are lucky to have fewer than one error for every 20 operations—and that means millions of errors an hour,” said Dr. Brown who also holds a position with the ARC Centre of Excellence for Engineered Quantum Systems.

“That’s a lot of dropped stitches.”

Most of the building blocks in today’s experimental quantum computers—quantum bits or qubits—are taken up by the “overhead” of error correction.

“My approach to suppressing errors is to use a code that operates across the surface of the architecture in two dimensions. The effect of this is to free up a lot of the hardware from error correction and allow it to get on with the useful stuff,” Dr. Brown said.

Dr. Naomi Nickerson is Director of Quantum Architecture at PsiQuantum in Palo Alto, California, and unconnected to the research. She said: “This result establishes a new option for performing fault-tolerant gates, which has the potential to greatly reduce overhead and bring practical quantum computing closer.”