No-go theorems for \psi-epistemic models based on a continuity assumption

TL;DR

This paper proves that under certain continuity and separability assumptions, -epistemic models cannot fully explain quantum states, providing a new constraint different from previous no-go theorems.

Contribution

It introduces a novel no-go theorem for -epistemic models based on a continuity assumption, applicable with a single quantum system.

Findings

-epistemic models are incompatible with quantum theory under the assumptions.

The proof is different from the Pusey-Barrett-Rudolph theorem.

It provides a constraint using only a single copy of the quantum system.

Abstract

The quantum state \psi is a mathematical object used to determine the probabilities of different outcomes when measuring a physical system. Its fundamental nature has been the subject of discussions since the inception of quantum theory: is it ontic, that is, does it correspond to a real property of the physical system? Or is it epistemic, that is, does it merely represent our knowledge about the system? Assuming a natural continuity assumption and a weak separability assumption, we show here that epistemic interpretations of the quantum state are in contradiction with quantum theory. Our argument is different from the recent proof of Pusey, Barrett, and Rudolph and it already yields a non-trivial constraint on \psi-epistemic models using a single copy of the system in question.