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Zenith Grant Awardee

Antonio Acín

The Institute of Photonic Sciences


Rafael Chaves, Freiburg University; Matty Hoban, Oxford University; Raymond Lal, Oxford University

Project Title

Quantum Bayesian networks: the physics of nonlocal events

Project Summary

Cause and effect are at the heart of science. We aim to explain observations through their causes, both direct and indirect. If we observe that certain occurrences always coincide, e.g. it getting both darker and cooler in the evening, they can often be explained by a common cause (the sun setting in our example). Quantum physics provides a major obstacle to understanding such correlated phenomena through a common cause explanation. This obstruction comes in the form of quantum non-locality, something Einstein called ‘spooky action at a distance’. The study of causality has been formalized in the past few decades within the field of computer science. The motivation for this study came from trying to understand how machines with artificial intelligence can reason about data they obtain in such a way to make informed decisions. Only very recently have there been earnest attempts to integrate research from this community into the study of quantum theory. The key question is now: how do we reason about quantum data and the correlations they exhibit? We aim to support a community of researchers that will address this very question.

Technical Abstract

The ability to infer causal relationships from empirical data is of central importance in science. Arguably it is the foundation of any quantitative and predictive discipline, including physical, behavioral, social and biological sciences. In spite of its crucial role, the mathematical theory of causality—a highly cross-disciplinary field at the intersection of computer science, machine learning and statistics— has only recently been given a firm theoretical basis. Remarkably, it also provides a fresh and almost unexplored new perspective for analyzing the counter-intuitive properties of quantum theory, in particular the phenomenon of quantum non-locality. Concepts and tools from the causal inference literature—in particular the graphical notation of Bayesian networks—provide an elegant and unifying framework for the study of non-locality beyond the usual established scenarios, a realization that is increasingly appreciated among quantum physicists. There is now clearly a community of researchers devoted to take this research program to the natural next step: the development of the theory of quantum Bayesian networks providing a mathematical framework for the physics of non-local events. The aim of this project is to support and expand this nascent field through funding travel and workshops.

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