$\psi$-Epistemic Models, Einsteinian Intuitions, and No-Gos. A Critical Study of Recent Developments on the Quantum State

TL;DR

This paper critically examines recent epistemic models of the quantum state, especially hidden variable approaches inspired by Einstein, analyzing their claims and the implications of no-go theorems on their validity.

Contribution

It provides a critical assessment of recent developments in epistemic quantum models, highlighting the limitations and interpretative challenges posed by no-go results.

Findings

No-go theorems do not definitively disprove epistemic models

The evidential support for certain models is less robust than previously thought

Achievements attributed to these models should be viewed with skepticism

Abstract

Quantum mechanics notoriously faces the measurement problem, the problem that if read thoroughly, it implies the nonexistence of definite outcomes in measurement procedures. A plausible reaction to this and to related problems is to regard a system's quantum state $|\psi\rangle$ merely as an indication of our lack of knowledge about the system, i.e., to interpret it epistemically. However, there are radically different ways to spell out such an epistemic view of the quantum state. We here investigate recent developments in the branch that introduces hidden variables $\lambda$ in addition to the quantum state $|\psi\rangle$ and has its roots in Einstein's views. In particular, we confront purported achievements of a concrete model that has been considered to serve as evidence for an epistemic view of the envisioned kind, as well as specific no-go results and their import. It will be argued that while an epistemic account of the particular kind is not straightforwardly ruled out by the no-go results, they demonstrate that the evidential character of the model(s) discussed rests on a rather shaky foundation, and that they make some achievements widely recognized in the literature appear worthy of doubt.