Information Causality as a physical principle

Marcin Pawłowski, Tomasz Paterek, Dagomir Kaszlikowski +3 more

Vishnu Purushothaman, Akarshit Baranwal, A. K. Pan

Tzyh Haur Yang, Daniel Cavalcanti, Mafalda L Almeida +2 more

We study the principle of information-causality (IC) in the presence of extremal no-signaling correlations on a tripartite scenario. We prove that all, except one, of the non-local correlations lead to violation of IC. The remaining non-quantum correlation is shown to satisfy any bipartite physical principle.

Mariami Gachechiladze, Nikolai Miklin

Information causality (IC) was introduced as a physical principle constraining correlations in non-signaling theories. Whether it can recover the exact quantum correlation boundary, beyond Uffink's inequality, has remained an open question. Here, we combine its generalized formulation for correlated inputs with a new communication protocol to derive quantum Bell inequalities that exactly characterize the quantum correlations in the simplest bipartite Bell scenario, with two binary measurements. In particular, we derive the Tsirelson-Landau-Masanes criterion directly from IC. Thus, the generalized IC implies macroscopic locality, while we also present macroscopically local correlations that violate the generalized IC. This establishes that generalized IC is a strictly stronger principle in this scenario. Together with our earlier result that generalized IC implies a nontrivial communication complexity principle, these findings strengthen the role of information causality in explaining the limits of quantum nonlocality and provide a systematic route to deriving tighter bounds on the set of quantum correlations in more general Bell scenarios.

Marcin Pawłowski, Tomasz Paterek, Dagomir Kaszlikowski +3 more

Information causality A broad class of theories exist which share the distinguishing characteristics of quantum mechanics, but allow even stronger correlations. Therefore a criterion that could be used to distinguish physical theories from non-physical ones would be of considerable value. The principle of 'information causality', introduced here by Marcin Pawłowski et al., may provide just this. The principle states that communication of m classical bits causes information gain of at most m bits. The authors show that it is respected by classical and quantum physics, but violated by other models that resemble quantum mechanics but with stronger correlations. The principle is a generalization of the no-signalling condition (information cannot be transmitted faster than light) and may be a foundational property of nature.

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