What's stopping us from building useful quantum computers? And how long until we'll have them?

Quantum computers often grab the science headlines. But what exactly is quantum computing? What will quantum computers be able to do, and when can we expect to have fully functional ones?

An untapped resource could provide the magic needed for quantum computation — and perhaps even open the door to time travel.

Here's a brief introduction to the possible future of computing.

Why it's hard to build quantum computers and what can be done about it.

Eleven makes multiplication easy.

The impossible becomes possible when you move into the third dimension.

A quick look at an ancient problem.

A mathematical "paradox" explains why more roads don't necessarily mean fewer traffic jams.

Why there are only three regular polygons you can tile a wall with.