Answer Geek: What Is a Quantum Computer?

<br> -- Q U E S T I O N: I’ve been hearing a lot about quantum technology and the possibility of developing a quantum computer thousands of times more powerful than any computer currently in existence. Could you describe, in layman’s terms, what a quantum computer is (or will be)?

— Jeff Byrne

A N S W E R: Oh boy. Here we go. Quantum computers. Answer Geeks hate questions about quantum computers. You want to know why? Because that means delving into the inexplicable world of quantum mechanics, where the normal laws of physics aren’t applicable, a single object can be said to exist in many states — every state — at once, and all is counterintuitive. Give us poor Answer Geeks gears and pistons. Or bits and bytes. Anything where objects act on each other in a predictable ways and cause and effect is easy to understand. But not quantum computers.

Atomic Power

Instead of the simple yes-or-no paradigm of conventional computers — where 1 is 1, 0 is 0 and everything gets crunched through a bunch of silicon switches in a nice, linear fashion — quantum computers use the fundamental building blocks of atoms themselves, subatomic particles such as electrons, protons and photons, and exploit the bizarre quantum rules that govern their behavior. These particles spin, so if the spin is one direction — up, for example — that could be the equivalent of the 1 in a conventional computer, while a particle with a down spin could be a 0. Simple so far.

According to the laws of quantum physics, though, there is no way to know with certainty whether a particle has an up spin or a down spin or something in between, so it is said to possess all of those properties all at the same time. This is called superposition, and it turns out to have very interesting ramifications for certain kinds computing, because while the bit in a conventional computer must equal either 1 or 0, a quantum bit — or “qubit” — can be both 1 and 0 at the same time.