Abstract

The “psi-epistemic” view is that the quantum state does not represent a state of the world, but a state of knowledge about the world. It draws its motivation, in part, from the observation of qualitative similarities between characteristic properties of non-orthogonal quantum wavefunctions and between overlapping classical probability distributions. It might be suggested that this gives a natural explanation for these properties, which seem puzzling for the alternative “psi-ontic” view. I will examine two such similarities, quantum state overlap and quantum state discrimination, and ask how far we can reproduce the quantitative values given by quantum theory. It will be shown that the psi-epistemic view cannot account for these values, and must instead rely on the same kind of explanations as the “psi-ontic” view.