Experimental implementation of a Kochen-Specker Set of Quantum Tests

Abstract

The conflict between classical and quantum physics can be identified through a series of yes-no tests onquantum 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 thatis free of the initialization problem that affects some quantum computers. Here, we report the firstexperimental implementation of a complete KS set that consists of 18 yes-no tests on four-dimensionalquantum systems and show how to use the KS set to obtain a state-independent quantum advantage. Wefirst demonstrate the unique power of this KS set for solving a task while avoiding the problem of stateinitialization. Such a demonstration is done by showing that, for 28 different quantum states encoded inthe orbital-angular-momentum and polarization degrees of freedom of single photons, the KS set providesan impossible-to-beat solution. In a second experiment, we generate maximally contextual quantumcorrelations by performing compatible sequential measurements of the polarization and path of singlephotons. In this case, state independence is demonstrated for 15 different initial states. Maximumcontextuality and state independence follow from the fact that the sequences of measurements projectany initial quantum state onto one of the KS set’s eigenstates. Our results show that KS sets can be usedfor quantum-information processing and quantum computation and pave the way for future developments.