Quantum Magic Tricks Q&A at the Royal Institution

Uploaded by InstituteofPhysics on 23.05.2012

Audience member: Hi, when we were doing the Nano engineering down here on the floor.
You seemed to be deliberately saying that you were destroying the electron on one atom and then recreating it somewhere else.
Can you just explain how that works as opposed to moving the electron?
Yvette: That's a really good question, I am really glad that you asked that. It all comes down to this very special equation which I eluded to called the Schrödinger equation.
There is a way in which we can, shall I say, recast that. So that we get what's known as an operative form of it. Which is basically what we did here today. So that form is that within how we explain that equation we can literally destroy a particle and create it again into another state.
And so it becomes part of the mechanics, the quantum mechanics of what we can actually do with our system. And all of that information is then put in at the equation level and out of that, like what we've got. We have got all these possibilities that can happen. And then we have to look at the quantum statistics that sit on top of that. So when I was saying when you take like a snapshot of an average of what's going on, that's basically what we do.
But to be a bit more specific about you question. We have to put a kinetic degree of freedom into our particles. And so our electrons so what they actually see in this model, they see the atomic like states they can be in. And the way in which the mechanics works in the model is that they get to move from atom to atom. But in order to be able to move and because we have to keep the same number of particles. We can't put more in our take them out of our system, we have to literally destroy them and create them elsewhere in our structure.
Audience member: Is nanotechnology, how's it powered? Where does it get the energy to do what it does?
Yvette: That's also a very good question. With a lot of these technologies... let's go back. For example, this one here. Let's have a look at this quantum dot.
Amazingly this little quantum dot is connected to the outside world by very, very tiny nano wires.
So this is part of the technology design we need to also be considering. You're right they can't be sort of live in isolation they need to be connecting somehow. I mean with the nanoparticles they don't so much need to be connected because if you've got an external magnetic field which is acting at a distance they can do their job very nicely, you just have to get them in the body. But some of the nanotechnologies do need to be connected to the outside world and you know that's sort of how we drive them. We can put little gate voltage across it and sort of drive the electrons in that way.