Breakthrough quantum computer instantly

 makes calculations that take rivals 47 years

James Titcomb

Google has developed a quantum computer that instantly makes calculations that would take the best existing supercomputers 47 years, in a breakthrough meant to establish beyond doubt that the experimental machines can outperform conventional rivals.

A paper from researchers at Google published online claims that the company’s latest technology is “beyond the capabilities of existing classical supercomputers”.

Proponents of quantum computers say the technology, which relies on the peculiar states of quantum physics, can create hugely powerful machines able to battle climate change and create breakthrough drugs.

However, they also threaten to undermine today’s encryption systems, making them a national security priority.

Four years ago, Google claimed to be the first company to achieve “quantum supremacy” – a milestone point at which quantum computers surpass existing machines.

This was challenged at the time by rivals, which argued that Google was exaggerating the difference between its machine and traditional supercomputers.

The company’s new paper – Phase Transition in Random Circuit Sampling – published on the open access science website ArXiv, demonstrates a more powerful device that aims to end the debate.

While the 2019 machine had 53 qubits, the building blocks of quantum computers, the next generation device has 70.

Adding more qubits improves a quantum computer’s power exponentially, meaning the new machine is 241 million times more powerful than the 2019 machine.

The researchers said it would take Frontier, the world’s leading supercomputer, 6.18 seconds to match a calculation from Google’s 53-qubit computer from 2019. In comparison, it would take 47.2 years to match its latest one.

The researchers also claim that their latest quantum computer is more powerful than demonstrations from a Chinese lab which is seen as a leader in the field.

Google’s paper demonstrates how larger quantum computers can manage “noise” – interference that threatens to disrupt the fragile states in which qubits operate – to continue to make calculations.

The researchers said: “We conclude that our demonstration is firmly in the regime of beyond-classical quantum computation.”

The rival machines were measured on a randomisation task that critics say favour quantum computers and lack any practical value beyond academic study.

Steve Brierley, the chief executive of Cambridge-based quantum company Riverlane, said: “This is a major milestone. The squabbling about whether we had reached, or indeed could reach, quantum supremacy is now resolved.”

Sebastian Weidt, the chief executive of Brighton-based start-up Universal Quantum, said quantum computers needed to demonstrate more practical functions.

He said: “This is a very nice demonstration of quantum advantage. While a great achievement academically, the algorithm used does not really have real world practical applications though.

“We really must get to utility quantum computing – an era where quantum computers with many thousand qubits actually begin to deliver value to society in a way that classical computers never will be able to.”