State-independent experimental test of quantum contextuality

TL;DR

This paper reports a state-independent experimental test of quantum contextuality using trapped ions, conclusively demonstrating the conflict with non-contextual hidden variable models without detection loopholes.

Contribution

It provides the first loophole-free, state-independent experimental verification of quantum contextuality with trapped ions, advancing foundational quantum physics research.

Findings

Demonstrated conflict with non-contextuality independent of quantum state

Achieved a loophole-free test using trapped ions

Results cannot be explained by non-contextual hidden variable models

Abstract

The question of whether quantum phenomena can be explained by classical models with hidden variables is the subject of a long lasting debate. In 1964, Bell showed that certain types of classical models cannot explain the quantum mechanical predictions for specific states of distant particles. Along this line, some types of hidden variable models have been experimentally ruled out. An intuitive feature for classical models is non-contextuality: the property that any measurement has a value which is independent of other compatible measurements being carried out at the same time. However, the results of Kochen, Specker, and Bell show that non-contextuality is in conflict with quantum mechanics. The conflict resides in the structure of the theory and is independent of the properties of special states. It has been debated whether the Kochen-Specker theorem could be experimentally tested at all. Only recently, first tests of quantum contextuality have been proposed and undertaken with photons and neutrons. Yet these tests required the generation of special quantum states and left various loopholes open. Here, using trapped ions, we experimentally demonstrate a state-independent conflict with non-contextuality. The experiment is not subject to the detection loophole and we show that, despite imperfections and possible measurement disturbances, our results cannot be explained in non-contextual terms.