Nikolai. Miklin: Quantifying causal influences in the presence of a quantum common cause
Channel: Centrum Fizyki Teoretycznej PAN
Date: 2021-08-12

Nikolai Miklin (Heinrich Heine University Düsseldorf). 
Quantifying causal influences in the presence of a quantum common cause.
Quantum mechanics challenges our intuition on the cause-effect relations in nature. Some fundamental concepts, including Reichenbach’s common cause principle or the notion of local realism, have to be reconsidered. Traditionally, this is witnessed by the violation of a Bell inequality. But are Bell inequalities the only signature of the incompatibility between quantum correlations and causality theory? Motivated by this question, we introduce a general framework able to estimate causal influences between two variables, without the need of interventions and irrespectively of the classical, quantum, or even postquantum nature of a common cause. In particular, by considering the simplest instrumental scenario—for which violation of Bell inequalities is not possible—we show that every pure bipartite entangled state violates the classical bounds on causal influence, thus, answering in negative to the posed question and opening a new venue to explore the role of causality within quantum theory.
Quantum Information and Quantum Computing Seminars CTP PAS
2021-05-13