michael_nielsen

It explains one of the most remarkable known applications of quantum computers: to search an N-item search space, they only need to examine the search space roughly the square root of N times.

This is, frankly, incredible. When I first heard the result, I couldn't imagine how it was possible. But it's true! The essay explains why it's true, how it's done, and even sketches how one might have come to discover the search algorithm.

The essay isn't just about the search algorithm. It's also about learning to think in the quantum realm. Think of it as an introduction to quantum algorithm design, introducing many techniques which can be used in other algorithms as well.