Rostock 2019 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 27: Quantum Information (Concepts and Methods) II

Q 27.5: Talk

Wednesday, March 13, 2019, 11:45–12:00, S HS 001 Chemie

Graph approach to quantum contextuality for projectors of nonunit rank — •Zhen-Peng Xu, Matthias Kleinmann, and Xiao-Dong Yu — University of Siegen, D-57068 Siegen, Germany

Quantum contextuality is the property of quantum theory that, in general, the outcome for a projector cannot be predicted without specifying the measurement context, i.e., which other projectors are measured alongside this projector. In this formulation of quantum contextuality, it is usually assumed that the measurements are composed of projectors of rank one, since the maximal amount of quantum contextuality can already be obtained under this restriction. However, measurements with high rank still can be beneficial, in particular they might allow for simpler examples of state-independent contextuality (SIC) than it is possible in the rank-one case. We develop methods to exhaustively search for SIC with projectors with nonunit rank, using a modification of the graph approach to contextuality. We find that for a low number of projectors there is no example for SIC with rank two projectors, but we also provide examples where SIC can only be realized by using nonunit rank projectors.