This was not just any math problem.

On Wednesday, Google said its researchers had performed a calculation that the largest supercomputers could not complete in under 10,000 years. And they had done it in 3 minutes 20 seconds.

With that calculation, the company said, its research lab in Santa Barbara, Calif., achieved a milestone that scientists had been working toward since the 1980s — a breakthrough called “quantum supremacy” that could allow new kinds of computers to do calculations at speeds that are inconceivable with today’s technology.

The long-sought breakthrough could have implications for national security and cryptography and even pave the way for the creation of new medicines. Here’s what you need to know about quantum computing and the importance of Google’s claim.

China and the U.S. see it as a matter of national security

Like all leaps in technology, quantum machines are a double-edged sword: Someday, they could power advances in artificial intelligence. But they could also overwhelm the encryption that protects computers vital to national security or even the e-commerce sites we all use everyday.