Vincenzo D'Ambrosio, Isabelle Herbauts, Elias Amselem, Eleonora Nagali, Mohamed Bourennane, Fabio Sciarrino, Adan Cabello
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 vs classical advantage, free of the initialization problem affecting quantum computers. Here we report the first experimental implementation of a complete KS set consisting of 18 yes-no tests on four dimensional quantum systems, and show how to use them to obtain state-independent quantum advantage. We first demonstrate the unique power of this KS set for solving a task avoiding the problem of state initialization. This 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 provide 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.
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http://arxiv.org/abs/1209.1836
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