TOM: I'm kind of expecting it to be this enormous bit of equipment that's sitting round here somewhere.
JACQUES: No, no, you're almost there. It's just in... this cupboard.
TOM: This cupboard!
JACQUES: So here is... the quantum computer.
TOM: That little chip there?
JACQUES: In fact, what it really is, is just this -- you see the very thin black strip
in the middle. That's actually the chip.
Most classical computers store information on big macroscopic things. And what we do
at the Centre for Quantum Photonics, and what other people are doing around the world, is
try to store that information on single particles. Or single atoms. In our case, we're going
to do it with photons, particles of light. And then you start inheriting the beautiful
rules of quantum physics.
TOM: So this is double-slit experiment, this is something that is a particle and a wave
at the same time.
JACQUES: And if you imagine these -- your two slits, and we say, well, a photon going
through the top slit is a 0, and a photon going through the bottom slit is a 1, now
when we run this experiment we've got the idea that we've got both a 0 and a 1 at the same time.
TOM: So by cleverly cancelling out those waves, adding them, you can kind of design an algorithm?
JACQUES: ...yeah. This is where it gets a bit tricker. Back in the olden days, when
you wanted to build a quantum computer, you needed big things like this. The problem with
this is that it gets a bit hot, and we maybe knock something, and it all misaligns. What
we do in Bristol is we've been designing and fabricating what we call waveguides. Now waveguides
are basically just bits of fibre-optic on chip, on a bit of glass.
TOM: Okay.
JACQUES: So we can actually manipulate the photons moving through a bit of silicon.
TOM: And so by changing how the waveguides act, you can change the photons --
the way the photons pass through the system.
JACQUES: Exactly.
TOM: And that's your programming? That's algorithm design...
JACQUES: That's our programming. So we're going to get our bit of glass, and we're going
to put a metal piece of conductor on top. And when we apply a voltage, it's going to
heat the thing up -- it's a heater...
TOM: Which changes how the waveguide acts...
JACQUES: Yeah! It changes the refractive index.
TOM: Which slows the light down.
JACQUES: Precisely.
TOM: Just a tiny amount but enough to change the interference pattern later on, because
we're dealing with the speed of light, the wavelengths involved are tiny tiny tiny...
JACQUES: Yes, exactly.
TOM: So a tiny bit of heating in the waveguide changes the interference pattern, changes
the quantum computer, that's your programming.
JACQUES: You got it. You got it!
TOM: There is a guy -- the person from the university who's just behind the camera, who
you can't see in the dark there, is just going "yes! he got it!"
JACQUES: It's online now. So what you can do is, you can go and play around with a simulation
of it, a model, and if you come up with an idea you can then ask to actually use it.
TOM: To use that?
JACQUES: And to put photons into it and to heat it up in real life. So it's there, for
people to use, it's called Quantum in the Cloud.
That's what we're getting excited about.
TOM: Jacques Carolan is from the Centre for Quantum Photonics at the University of Bristol.
Jacques, thank you very much.
JACQUES: Thank you very much, Tom.