This is from the FT (behind a paywall) so it came to me via Charles Arthur’s invaluable The Overspill:

A paper by Google’s researchers seen by the FT, that was briefly posted earlier this week on a Nasa website before being removed, claimed that their processor was able to perform a calculation in three minutes and 20 seconds that would take today’s most advanced classical computer, known as Summit, approximately 10,000 years.

The researchers said this meant the “quantum supremacy”, when quantum computers carry out calculations that had previously been impossible, had been achieved.

“This dramatic speed-up relative to all known classical algorithms provides an experimental realisation of quantum supremacy on a computational task and heralds the advent of a much-anticipated computing paradigm,” the authors wrote.

“To our knowledge, this experiment marks the first computation that can only be performed on a quantum processor.”

The system can only perform a single, highly technical calculation, according to the researchers, and the use of quantum machines to solve practical problems is still years away.

But the Google researchers called it “a milestone towards full-scale quantum computing”. They also predicted that the power of quantum machines would expand at a “double exponential rate”, compared to the exponential rate of Moore’s Law, which has driven advances in silicon chips in the first era of computing.

Interesting that the article was withdrawn so precipitously. But really significant if true. After all, current encryption methods are all based on the proposition that some computations are beyond the reach of conventional machines.