# Quantum computers and freaky physics

Ever been told you can’t have it both ways? Well, the next time anyone says it to you, you can tell them they’re wrong. In fact we don’t mind if you look a bit smug while you say it – give them a curl of your lip and a pitying eye roll. You’ll want to explain that having it both ways is what makes the universe work, actually, and it’s the basis for one of the next big advancements in computer science. Then give a satisfied smile, and see if the person has fallen madly in love with you yet. Really? Oh.

We’re terribly sorry, we shouldn’t be goading you into being so horrid. We’ll stop now. But everything we’re saying is true – having it both ways is part of quantum mechanics, our best guess at understanding how the universe works at its deepest level. It’s thoroughly weird and contradictory, and computers are preparing to take advantage of it.

## One way or another?

The bit that makes quantum mechanics useful in computers just happens to be what makes it so weird. It’s also why you can have it both ways, for a little while anyhow. It’s all to do with states of being. In quantum mechanics, particles (like electrons and photons) can exist in one state or another, or in two states at the same time. That means that different things about those particles can be true at once. For example, if you’re trying to work out the flight path of a photon or particular properties of an electron, you can’t – different answers are true at the same time. At least, that is, until you look at it. That’s because when you check to see what the final answer is, you force the particle to pick a definite state and all the other states vanish, never to come back.

Regular computers put things in states too. Everything you’ve got on a computer is made out of bits, which are just zeros and ones. Nothing else – each bit is one or the other. It’s called binary code. A computer combines bits of binary to store things in memory and moves them around to do calculations. This is where the researchers hope to bring the freaky particles of quantum mechanics into play. If a computer could work in a quantum way, then a bit could be a zero and a one at the same time!

That state of being both at the same time is called superposition, and you’d only need to use a small number of particles in superposition to work with a lot of information. Only 1000 particles could store all the numbers from 1 to – well, it won’t fit on this page but it’s about 300 digits long. Manipulate your particles with a few well-placed lasers and hang on tight, because you’re quantum computing my friend.