Prof. Dr. David Gross (U Köln): Quantum correlations and causal structures

Veranstalter:in : FB01, Prof. Dr. Claus Lämmerzahl
Ort : Hörsaal H3, Geb. NW1, Otto-Hahn-Allee 1
Beginn : 13. Juli 2023, 16:00 Uhr
Ende : 13. Juli 2023, 17:00 Uhr

Prof. Dr. David Gross (U Köln)

 Quantum correlations and causal structures

 Today, one can routinely perform experiments that lead to correlations that are fundamentally incompatible with the classical concept of reality. (C.f. the 2022 Nobel Prize). In the first part of the talk I will remind you how -- without even accepting the validity of quantum mechanics -- the mere existence of such correlations has far-reaching implications. In particular, they show that there is true randomness, and that it is impossible to clone general physical systems. In a second part, I will talk about a recent line of research that combines quantum correlations with the study of causal structures. A causal structure is a description of the functional dependencies between random variables. In both classical and quantum probability theory, it is a fundamental but difficult problem to decide whether an observed distribution is compatible with a given causal structure. We have recently found first complete sets of tests for some such quantum causal compatibility problems, based on the so-called "quantum inflation hierarchy" of semi-definite programs [arXiv:2110.14659, arXiv:2212.11299]. I will introduce the problem, its significance, and sketch the technical results.