On the reality of the quantum state once again: A no-go theorem for $\psi$-ontic models

TL;DR

This paper proves that $$-ontic models cannot replicate quantum mechanics by showing all pure states must be orthogonal, which contradicts quantum theory, challenging the existing categorization of hidden variable models.

Contribution

It demonstrates that $$-ontic models are incompatible with quantum mechanics using information-theoretic arguments, highlighting issues with the HS categorization of hidden variable models.

Findings

$$-ontic models require orthogonal pure states, conflicting with quantum superposition.

The HS categorization of hidden variable models is incomplete and problematic.

Both $$-ontic and $$-epistemic models are incompatible with quantum theory.

Abstract

In this paper we show that $\psi$-ontic models, as defined by Harrigan and Spekkens (HS), cannot reproduce quantum theory. Instead of focusing on probability, we use information theoretic considerations to show that all pure states of $\psi$-ontic models must be orthogonal to each other, in clear violation of quantum mechanics. Given that (i) Pusey, Barrett and Rudolph (PBR) previously showed that $\psi$-epistemic models, as defined by HS, also contradict quantum mechanics, and (ii) the HS categorization is exhausted by these two types of models, we conclude that the HS categorization itself is problematic as it leaves no space for models that can reproduce quantum theory.