I think the issue is that the word "challenge" has two common usages in English: 1. to engage in competition 2. to dispute the truth or validity of And the a

I think the issue is that the word "challenge" has two common usages in English: 1. to engage in competition 2. to dispute the truth or validity of And the article uses the word in both senses -- the headline is that Chinese physicists are challenging Google in the first sense. But the article body mentions that other researchers have challenged the Google result in the second sense. Overall, it seems like a confusing choice of words by whoever wrote the headline.