Introduction

“When you come to a fork in the road, take it!” This sage advice from Yogi Berra revealed that he was not only a great baseball player and humorist, but also a secret quantum physicist. After all, everyday experience tells us that when you come to a fork in the road, you can go in one direction or the other. Only in the weird world of quantum physics can both paths be taken at the same time.

At least, that is, until someone sees you doing it. At that point you’ll suddenly find yourself on one side or the other. Either that, or you’ll end up in a pair of parallel universes simultaneously. (Physicists honestly can’t say which for sure.) This is but one of the fabulous mysteries of the universe according to the laws of quantum physics.

Brace yourself, however. For, in the words of Richard Feynman, another quantum giant, “I think I can safely say that nobody understands quantum physics.”