IBM casts doubt on Google’s claims of quantum supremacy | Science

Google researchers in Santa Barbara, California, say their advance may lead to near-term applications of quantum computers.

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*Update, 23 October, 5:40 a.m.: A study from Google claiming quantum supremacy, accidentally leaked online last month, has now been published in Nature. The Google group reiterates its claim that its 53-qubit computer performed, in 200 seconds, an arcane task that would take 10,000 years for Summit, a supercomputer IBM built for the Department of Energy that is currently the world’s fastest. But IBM appears to have already rebutted Google’s claim. On 21 October, it announced that, by tweaking the way Summit approaches the task, it can do it far faster: in 2.5 days. IBM says the threshold for quantum supremacy—doing something a classical computer can’t—has thus still not been met. The race continues. Read our 23 September story here:

The age of quantum computing may have begun not with a flashy press conference, but with an internet leak. According to a paper posted briefly—and presumably mistakenly—to a lab site, physicists at Google have used a quantum computer to perform a calculation that would overwhelm the world’s best conventional supercomputer. Although the specific computation has no known use, the result means scientists have passed a milestone known as “quantum supremacy.”

“It’s a great scientific…

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