Question: how to do you make a computer shining lasers on diamonds

Philip Dolan answered on 13 Jun 2011:

Normal computers use 1′s and 0′s (known as ‘bits’). In your computer’s hard disk this is a tiny little magnet that points up or down. In the processor this is a little circuit that either lets electricity flow, or stops it.

Quantum mechanics (this is a theory that you might learn a little bit about in sixth form) allows us to put something into two states at the same time. But it has to be something really small (like an electron might be in two places at once). It’s also really tough to do, cause if anything bumps into the electron it suddenly decides which of the two places it’s in.

This means we’d need to stop air molecules (they’re thrashing around your classroom right now like crazy) light, so it’d have to be completely pitch black, and absolutely everything else from disturbing it (even things like mobile phone signals, TV signals, sounds, and vibration).

If we do manage to keep it in 2 places at once, then it’s like a ’1′ and a ’0′ at the same time.

So for 1 ‘quantum bit’ or qubit’ you’d need 1 pair of ‘bits’ (in a regular computer), a ’1′ and ’0′.

But for 2 ‘qubits’ we kinda have lots of ways of arranging the 1′s and 0′s. We can have
1 – 1,
1 – 0,
0 – 1,
0 – 0.

So we’d need 4 pairs bits in a regular computer.

For 3 ‘qubits’ you’d need
1-1-1,
1-1-0,
…,
etc,
0-0-0.
In total – 8 pairs of bits.

If you have 4 qubits, 16 pairs of regular bits. By the time we have 30 qubits you’d need 1, 073, 741, 824 regular pairs to show all of the combinations. If we could have a quantum computer with 300 qubits (this might only be 300 electrons kept in their delicate ‘two-states-at-one-time) it’d take all of the atoms in the universe to represent all of the combinations!

The key to it all is keeping the electrons from bumping into anything. So we use the diamond as a kind of cage, to keep everything else out, and keep our electrons in their delicate two-states-at-one-time. We use the lasers to delicately nudge the electrons into being in two places at once.

I hope that made (a little) sense!

It’s really a very tough idea to explain, even to other scientists so don’t worry if it seems difficult.

Thanks for asking tho!

Phil