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Sufficient conditions for three-particle entanglement and their tests in recent experiments

Michael Seevinck·Jos Uffink
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Abstract

We point out a loophole problem in some recent experimental claims to produce three-particle entanglement. The problem consists in the question whether mixtures of two-particle entangled states might suffice to explain the experimental data. In an attempt to close this loophole, we review two sufficient conditions that distinguish between N-particle states in which all N particles are entangled to each other and states in which only M particles are entangled (with M<N). It is shown that three recent experiments to obtain three-particle entangled states (Bouwmeester et al., Pan et al., and Rauschenbeutel et al.) do not meet these conditions. We conclude that the question whether these experiments provide confirmation of three-particle entanglement remains unresolved. We also propose modifications of the experiments that would make such confirmation feasible.

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Michael Seevinck, Jos Uffink. 2002-02-08. Sufficient conditions for three-particle entanglement and their tests in recent experiments. https://doi.org/10.1103/physreva.65.012107

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