Experimental refutation of a class of \psi-epistemic models

TL;DR

This paper experimentally tests and refutes a class of -epistemic models of quantum states using high-dimensional optical states, supporting the view that the quantum state has an ontic nature.

Contribution

It provides an experimental refutation of continuous -epistemic models under realistic conditions, strengthening the ontic interpretation of the quantum state.

Findings

Experimental results agree with quantum theory predictions.

Constraints are placed on a class of -epistemic models.

The experiment accounts for realistic imperfections in state preparation and measurement.

Abstract

The quantum state is a mathematical object used to determine the outcome probabilities of measurements on physical systems. Its fundamental nature has been the subject of discussions since the origin of the 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? Recent advances in the foundations of quantum theory show that epistemic models that obey a simple continuity condition are in conflict with quantum theory already at the level of a single system. Here we report an experimental test of continuous epistemic models using high-dimensional attenuated coherent states of light traveling in an optical fibre. Due to non-ideal state preparation (of coherent states with imperfectly known phase) and non-ideal measurements (arising from losses and inefficient detection), this experiment only tests epistemic models that satisfy additional constraints which we discuss in detail. Our experimental results are in agreement with the predictions of quantum theory and provide constraints on a class of \psi-epistemic models.