Sure. Yeah. So we build quantum computers that we've known for a long time that is possible scientifically. 

It's incredibly difficult to build actual real machines that do this. But the technology is getting better and better. And when it gets to a certain level of advancement, it's going to be able to do computing that you can't currently do with the technology we currently have. 

What it really is, is that you're trying to do computing with systems which perfectly obey quantum mechanics at all times during the calculation. 

And that's actually a very, very difficult thing to engineer because you need to engineer sort of perfection in the technology as it runs a calculation. 

So it's very difficult to do that. It's all about kind of controlling errors, and correcting errors in a way that quantum mechanics is obeyed during the calculation.