Experimental Test of Irreducible Four-Qubit Greenberger-Horne-Zeilinger Paradox

Abstract

Bell's theorem shows a profound contradiction between local realism and quantum mechanics on the level of statistical predictions. It does not involve directly Einstein-Podolsky-Rosen (EPR) correlations. The paradox of Greenberger-Horne-Zeilinger (GHZ) disproves directly the concept of EPR elements of reality, based on the EPR correlations, in an all-versus-nothing way. A three-qubit experimental demonstration of the GHZ paradox was achieved nearly twenty years ago, and followed by demonstrations for more qubits. Still, the GHZ contradictions underlying the tests can be reduced to three-qubit one. We show an irreducible four-qubit GHZ paradox, and report its experimental demonstration. The reducibility loophole is closed. The bound of a three-setting per party Bell-GHZ inequality is violated by $7\sigma$. The fidelity of the GHZ state was around $81\%$, and an entanglement witness reveals a violation of the separability threshold by $19\sigma$.

arXiv comment6 pages, 4 figures, 1 table

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Cited by in corpus (5)

• Mermin inequalities for perfect correlations in many-qutrit systems
• Precise detection of multipartite entanglement in four-qubit Greenberger--Horne--Zeilinger diagonal states
• Device-independent Verification of Quantum Coherence without Quantum Control
• Greenberger-Horne-Zeilinger test for multi-dimension and arbitrary time nodes entangled histories
• Deterministic all-versus-nothing proofs of Bell nonlocality based on non-stabilizer states