Testing real quantum theory in an optical quantum network

Abstract

Quantum theory is commonly formulated in complex Hilbert spaces. However, the question of whether complex numbers need to be given a fundamental role in the theory has been debated since its pioneering days. Recently it has been shown that tests in the spirit of a Bell inequality can reveal quantum predictions in entanglement swapping scenarios that cannot be modelled by the natural real-number analog of standard quantum theory. Here, we tailor such tests for implementation in state-of-the-art photonic systems. We experimentally demonstrate quantum correlations in a network of three parties and two independent EPR sources that violate the constraints of real quantum theory by over $4.5$ standard deviations, hence disproving real quantum theory as a universal physical theory.

9 pages, 6 figures

References in corpus (4)

• Bounding the set of quantum correlations
• Beyond Bell's Theorem: Correlation Scenarios
• Simulating quantum systems using real Hilbert spaces
• Efficiency of higher dimensional Hilbert spaces for the violation of Bell inequalities

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