The claim, made in a new scientific paper, is the most serious indication yet that the promise of quantum computers—an emerging but unproven type of machine—is becoming reality, including their potential to solve formerly ungraspable mathematical problems.

Essentially, Google purports to have pulled off a stunt on a quantum computer that no classical machine—not even the world's most powerful supercomputer—can replicate.

Fortune obtained a copy of Google's paper, which was posted to NASA.gov earlier this week before being taken down. The Financial Times first reported the news.

A Google spokesperson declined to confirm the authenticity of the paper and its results. NASA did not respond immediately to a request for comment.