Experimental test of non-local causality
With the Bell loopholes finally closed, it’s time to explore new horizons in foundations. In this work we looked at inequalities that show an incompatibility between quantum mechanics and what we call non-local causality — i.e. local causality as in Bell’s theorem but with the additional twist of allowing some non-local causation from Alice’s to Bob’s outcome (or vice versa). Ours was one of the first experiments using the in this context relatively new toolbox of causal interventions.
Measurements on the reality of the wavefunction
Perhaps the first major breakthrough in quantum foundations (gravity related things aside) since Bell's theorem, it was shown in 2014 that there is a way to experimentally distinguish between epistemic and ontic interpretations of the quantum wavefunction. The experiment we carried out on a photonic ququart set new benchmarks for precision, imposed by very stringent theory requirements.
