Berlin 2014 – wissenschaftliches Programm

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SYQE: Symposium Quantum Correlations Beyond Entanglement

SYQE 2: Quantum Correlations Beyond Entanglement II

SYQE 2.2: Hauptvortrag

Dienstag, 18. März 2014, 17:00–17:30, Kinosaal

Quantum correlations on indefinite causal structures — •Caslav Brukner — Faculty of Physics, University of Vienna, Austria — Institute for Quantum Optics and Quantum Infromation, Austrian Academy of Sciences, Austria

In quantum physics it is standardly assumed that the background time or definite causal structure exists such that every operation is either in the future, in the past or space-like separated from any other operation. I will present a framework that assumes that operations in local laboratories are described by quantum theory (i.e. are completely-positive maps), but where no reference is made to any causal relations between the operations in the laboratories. Remarkably, the framework allows for correlations that are not causally ordered (i.e. one cannot say that one operations is before or after the other), as demonstrated by the violation of "causal inequality". I will show that the violation of the inequality is upper bounded by a bound (analogous to the "Tsirelson's bound") that is lower than what is algebraically possible and discuss interferometric experiments involving "superpositions of quantum circuits with definite causal structures".