A quantum advantage for inferring causal structure

作者：Ried Katja^*; Agnew Megan; Vermeyden Lydia; Janzing Dominik; Spekkens RobertW; Resch Kevin J

来源：Nature Physics, 2015, 11(5): 415-421.

DOI：10.1038/NPHYS3266

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.

• 出版日期2015-5