Brian Resnick in Vox:
Scientists at Google on Wednesday declared, via a paper in the journal Nature, that they’d done something extraordinary. In building a quantum computer that solved an incredibly hard problem in 200 seconds — a problem the world’s fastest supercomputer would take 10,000 years to solve — they’d achieved “quantum supremacy.” That is: Google’s quantum computer did something that no conventional computer could reasonably do.
Computer scientists have seen quantum supremacy — the moment when a quantum computer could perform an action a conventional computer couldn’t — as an elusive, important milestone for their field. There are many research groups working on quantum computers and applications, but it appears Google has beaten its rivals to this milestone.
According to John Preskill, the Caltech particle physicist who coined the term “quantum supremacy,” Google’s quantum computer “is something new in the exploration of nature. These systems are doing things that are unprecedented.”