 Pusey–Barrett–Rudolph theorem

Under preparation independence, an ontological model of a quantum system reproducing exact quantum quantum measurement probabilities cannot assign overlapping preparation measures to distinct pure states. An exclusion quantum measurement on independent copies makes every outcome impossible for one possible preparation; a common ontic region would require every response to vanish there. Thus the conclusion is a psi-ontic model, not a blanket exclusion of hidden variables or all informational interpretations.

The Pusey–Barrett–Rudolph (PBR) theorem is a result in quantum mechanics that addresses the interpretation of quantum states and their relationship to physical reality. Proposed by Matthew Pusey, Jonathan Barrett, and Nicolas Rudolph in 2012, the theorem argues against certain interpretations of quantum mechanics, particularly those that claim that quantum states merely represent knowledge about an underlying reality rather than representing a physical reality itself.