http://www.sciencemag.org/news/2019/10/ibm-casts-doubt-googles-claims-quantum-supremacy

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

*Update, 23 October, 5:40 am: A study from Google claiming quantum supremacy, accidentally leaked online a month ago, has now been published in Nature. The Google group reiterates its claim that, in 200 seconds, its 53-qubit computer performed 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 that a classical computer can’t—has thus still not been met. The race continues. Read our earlier story: