Reality of the quantum state: Towards a stronger {\psi}-ontology theorem

Understand

The Pusey-Barrett-Rudolph (PBR) no-go theorem provides an argument for the reality of the quantum state by ruling out {\psi}-epistemic ontological theories, in which the quantum state is of a statistical nature.

• It applies under an assumption of preparation independence, the validity of which has been subject to debate.
• We propose two plausible and less restrictive alternatives: a weaker notion allowing for classical correlations, and an even weaker, physically motivated notion of independence, which merely prohibits the possibility of superluminal causal influences in the preparation process.
• The latter is a minimal requirement for enabling a reasonable treatment of subsystems in any theory.