Matteo Fadel - Paradoxical entanglements

Prix Schläfli 2019 in Physics

A labyrinth of mirrors, a shiny pot, countless cables and digital displays. Visiting Matteo Fadel at his workplace at the University of Basel, he first takes us to the laboratory where he tracks strange quantum phenomena. Somewhere in the midst of all this apparatus, several hundred atoms are trapped and brought into a state that still causes physicists a lot of headaches today.

Matteo Fadel: Prix Schläfli 2019 Physik
Image: Universität Basel

In our subsequent conversation on the institute's terrace, we quickly sense that the matters being grappled with are always physically tangible yet also philosophically tricky - Fadel has been practising this balancing act for a long time. Even his Bachelor's thesis revolved around a paradox, known as "the black hole information loss problem". And now, quantum physics. Some paradoxes have made it into popular culture, others are famous mainly among experts. These include the EPR paradox, named after a triumvirate of theoretical physicists: Einstein, Podolsky and Rosen. It describes the entangled state of two particles, which retain this entanglement even when moved some distance apart - causing problems with Heisenberg's uncertainty principle. Einstein and his colleagues formulated it as a thought experiment to show how our understanding of contemporary physics leads to dead ends. Nowadays, this thought experiment has long since made its appearance in physics laboratories, including on the laboratory bench in Basel. Together with his colleagues, Fadel has been able to show for the first time that the EPR paradox can also be observed in a multi-particle system, for which he has now been awarded the Prix Schläfli. The findings were also published in the renowned journal Science, with Fadel as lead author. Was he surprised to receive this early honour? The answer reveals a healthy self-confidence, even if given in a very modest tone: "When you see a result, of course you know what it's worth."

Fadel is bothered that theoretical and experimental physics are so strictly separated

In order to achieve this result, Fadel not only had to penetrate deep into the theoretical construct of quantum physics, he also had to learn how to set up an experiment that makes such an observation possible at all. It is this talent in two areas that makes Fadel's work so special, and the fact that he takes both equally seriously becomes apparent when, after showing us his equipment with all the pride of a model railway enthusiast, he then tries to explain over coffee why quantum physics is much more than an intellectual playground for paradox-lovers. He is bothered by the fact that theoretical and experimental physics are usually so strictly separated. It's certainly not wrong to specialise, he says, but that's how you lose sight of the big picture. And it almost sounds a little coy when he explains that of course he has to spend a lot of time on theory as well as on practical skills - and therefore cannot be quite as good in either field as colleagues who decide for one or the other. Still, it was enough to get him a paper in a high-profile publication.

Matteo Fadel: Prix Schläfli 2019 Physik
Matteo Fadel: Prix Schläfli 2019 PhysikImage: Universität Basel