Introduction

We are an experimental quantum optics group run by Kevin Resch, based in the Department of Physics & Astronomy and the Institute for Quantum Computing at the University of Waterloo.

Quantum caus…………ality in Nature Physics

Our article, A quantum advantage for inferring causal structure, by Katja Reid, Megan Agnew, Lydia Vermeyden, Dominik Janzing, Rob Spekkens, and Kevin Resch just appeared in Nature Physics.  Giulio Chirabella wrote a News and Views piece on it entitled, Quantum information: Good causes.

Abstract: The problem of inferring causal relations from observed correlations is relevant to a wide variety of scientific disciplines. Yet given the correlations between just two classical variables, it is impossible to determine whether they arose from a causal influence of one on the other or a common cause influencing both. Only a randomized trial can settle the issue. Here we consider the problem of causal inference for quantum variables. We show that the analogue of a randomized trial, causal tomography, yields a complete solution. We also show that, in contrast to the classical case, one can sometimes infer the causal structure from observations alone. We implement a quantum-optical experiment wherein we control the causal relation between two optical modes, and two measurement schemes—with and without randomization—that extract this relation from the observed correlations. Our results show that entanglement and quantum coherence provide an advantage for causal inference.

Stories on IQC website here and Perimeter Institute website here.

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