Quantum leap? Row as rivals doubt Google's claim of real milestone in physics
In the perplexing world of quantum physics it is quite normal for matter to inhabit two places at once.
So it is fitting that Google's claim to have built a quantum computer that dramatically outpaces classical machines currently exists in a simultaneous state between dazzling success and non-achievement.
Yesterday, the internet giant announced it had reached "quantum supremacy" after its system - named Sycamore - took a little over three minutes to execute a task that would have kept the world's best supercomputers busy for 10,000 years.
The term "quantum supremacy" was first coined in 2012 by Prof John Preskill, the American theoretical physicist, of Caltech, to describe the moment that quantum computers can do things that classical computers cannot. Yet by its very nature quantum computing only works when you're not looking at it, and experts at IBM claim that if you stare too long at the latest claim, it begins to unravel.
The row centres around the task that Google asked its quantum computer to undertake and the computing power it was tested against.
Google said it had chosen a random number-generating problem which was difficult and prohibitively time-consuming for a classical machine. But in a technical paper and blog post IBM has shown that it is possible on a normal computer if it has enough storage.
The company's own supercomputer - named Summit - solved it in just two-and-a-half days. If true, it would still prevent Google claiming to have made a literal "quantum leap". Yet while IBM's claims have not yet been peer-reviewed, Google published its results in 'Nature' yesterday.
Jonathan Oppenheim, professor of quantum theory at University College London, said: "I think it's an important milestone, but useful quantum computing is decades away."
Writing in 'Nature', William Oliver, professor of the practice of physics at MIT, likened it to the first flight of the Wright Brothers. "It is what the event represented, rather than what it practically accomplished, that was paramount," he said.
While computer bits can only operate as "0" or "1", quantum bits (qubits) can exist in multiple states.
Qubits are made from tiny particles, such as the electrons of phosphorus atoms, that point magnetic north or south, but also multiple directions in between.
While pointless for tasks such as running word processors or web streaming, they could help break encryptions or simulate complex biological processes.