Welcome to the Quanta Science podcast.

Each episode, we bring you stories about developments in science and mathematics.

I'm Susan Vallett.

Researchers have proved that secure quantum encryption is possible in a world without hard problems. That's next.

It's season three of the joy of why, and I still have a lot of questions. Like, what is this

thing we call time? Why does altruism exist? And where is Jan

11? I'm here. Astrophysicist and co-host. Ready for anything. That's right. I'm bringing in the

A team. So brace yourselves. Get ready to learn. I'm Janelleleven. I'm Steve Strogatz.

And this is Quantum Magazine's podcast, The Joy of Why. New episodes drop every other Thursday.

Say you want to send a private message, cast a secret vote, or sign a document securely. If you do any of these tasks on a

computer, you're relying on encryption to keep your data safe. That encryption needs to withstand

attacks from codebreakers with their own computers. That's why modern encryption methods

rely on assumptions about what mathematical problems are hard for computers to solve.

But as cryptographers laid the mathematical foundations for this approach to information security in the 1980s,

a few researchers discovered that computational hardness wasn't the only way to safeguard secrets.

Quantum theory was originally developed to understand the

physics of atoms, but it also turned out to have deep connections to information and cryptography.

Researchers found ways to base the security of a few specific cryptographic tasks directly on the

laws of physics. However, these tasks were strange outliers. For all others,

there seemed to be no alternative to the classical computational approach. By the end of the

millennium, quantum cryptography researchers thought that was the end of the story. But in just the

past few years, the field has undergone

...