Anton Zeilinger is long retired, but is still active in research. The Nobel Prize in Physics, which he has now received, does not stop him from doing so. He receives it for his work on light particles, which he ‘entangles’ with each other: they share a quantum mechanical state, even if they are far from each other. Measurements on one particle directly affect the other, an effect Albert Einstein dismissed as “ghostly action at a distance” – but it is real, as Zeilinger’s research shows, among other things. Time for a short chat.
SZ: Congratulations on the Nobel Prize. You’ve been considered a candidate for a long time, so it can’t really have been a surprise, right?
Anton Zeilinger: It’s possible, but if it happens, you’ll be shocked.
Why did you start working with light particles in the 1990s? At the beginning of your career you still had to deal with neutrons.
Entanglement has always been my goal, it has fascinated me since the 1970s. But that is hardly possible with neutrons.
It also does not seem easy to bind two light particles together in such a way that they share a state and from that moment on remain coupled to each other over any distance.
At first glance it seems demanding, but over time we realized that more and more can be left out, our structure became simpler and easier.
And how can you teleport with these entangled particles?
I want to teleport the state of particle one. For this I produce an entangled state of two other particles, particle two and particle three. Then I entangle particles one and two. This transfers the state from particle one to particle three.
And what becomes of particle one?
That loses its personality because it gets caught up in part two. Particle three, on the other hand, is free and has taken over the state of particle one.
Complicated. Are you really getting on your nerves that everyone’s talking about “Star Trek” right now?
I’ve gotten used to this being a hook for a lot of people. But I often lecture, and people are always enthusiastic about physics.
Me too. That remains fascinating, even after almost 30 years. And I hope to make more exciting discoveries.
Today your research has found many applications, including commercial ones, for example in quantum encryption. Did you expect that?
No absolutely not. We just wanted to see what happens. In the beginning, quantum cryptography was considered a gimmick, I never imagined that so much money would flow into it these days.
You have also worked on quantum cryptography yourself.
Yes, we pushed that to show what can be made of it. But when it comes to industrial application, I’ve always withdrawn. You only have one head, and it can handle dollars or quantum particles, neither is possible.