Interview conducted with Thad Walker, UW-Madison physics professor.
DC: What are physicists currently doing with quantum mechanics?
Thad Walker: The theory of quantum mechanics explains essentially everything about our world that we know about. But it makes some bizarre predictions.
Since technologies are now good enough, we can really start testing those bizarre predictions. One of the things that distinguished low-energy physics in the last 10 or 15 years is trying to push the limits of what quantum mechanics allows us to do.
DC: How is quantum mechanics different from day-to-day physics?
TW: Every quantum particle is identical to every other one. If you're looking at two quantum particles and they trade places, you don't know that they did that. There is no way for you to tell this oxygen atom from this oxygen atom. They are identical.
The primary feature of quantum mechanics being used in our studies—[called entanglement]—is that if you take two quantum systems and let them interact and then pull them apart from each other, a measurement on one of them will tell you what the state of the other is, without looking at it.
These are the kinds of things that classical intuition says you can't do. Yet people have done tons of experiments showing that is in fact how the world works.
DC: So how does this sort of physics apply to everyday stuff outside the lab?
TW: The security of our entire information infrastructure is based on certain kinds of codes being difficult to break. Quantum theory predicts that it should be possible to build a quantum computer that can break those codes much more easily.
That's why the government would like for us to have [a quantum computer] before anybody else does. You definitely don't want other people to be able to do it and you not do it.
But nobody yet knows how to build a quantum computer that's big enough to do anything interesting. You need individual quantum systems you can manipulate with high precision, that can interact with each other in a controlled quantum manner.
The interesting part of it is we're learning how to [make a quantum computer] right now. If we had the technology to physically realize a quantum computer, we know how to run it. The protocols [and algorithms] have been worked out, to an extent. It's not a closed area of research by any means.
But if you're thinking that we're going to see a quantum computer on every desk, no. It doesn't solve those problems any better than a regular computer. On the other hand, when the digital computer was invented, people had in mind using it to solve scientific problems [and not the things it does now, like word processing]. So, who knows?
The quantum manipulation of matter is enormously important. It's an area of research that nobody really knows where it's going to go. We're probing the universe with quantum mechanics.
