Experimental implementation of a Kochen-Specker set of quantum tests

TL;DR

This paper reports the first experimental implementation of a complete Kochen-Specker set of 18 yes-no tests on four-dimensional quantum systems, demonstrating a state-independent quantum advantage and generating maximally contextual correlations.

Contribution

It provides the first experimental realization of a complete KS set for quantum tests, showing quantum advantage without state initialization and generating contextual correlations.

Findings

KS set enables state-independent quantum advantage

Experimental demonstration on single photons with orbital-angular-momentum and polarization

Generation of maximally contextual quantum correlations

Abstract

The conflict between classical and quantum physics can be identified through a series of yes-no tests on quantum systems, without it being necessary that these systems be in special quantum states. Kochen-Specker (KS) sets of yes-no tests have this property and provide a quantum-versus-classical advantage that is free of the initialization problem that affects some quantum computers. Here, we report the first experimental implementation of a complete KS set that consists of 18 yes-no tests on four-dimensional quantum systems and show how to use the KS set to obtain a state-independent quantum advantage. We first demonstrate the unique power of this KS set for solving a task while avoiding the problem of state initialization. Such a demonstration is done by showing that, for 28 different quantum states encoded in the orbital-angular-momentum and polarization degrees of freedom of single photons, the KS set provides an impossible-to-beat solution. In a second experiment, we generate maximally contextual quantum correlations by performing compatible sequential measurements of the polarization and path of single photons. In this case, state independence is demonstrated for 15 different initial states. Maximum contextuality and state independence follow from the fact that the sequences of measurements project any initial quantum state onto one of the KS set's eigenstates. Our results show that KS sets can be used for quantum-information processing and quantum computation and pave the way for future developments.