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تسجيل مستخدم جديدExperimental Test of Generalized Hardys Paradox
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Since the pillars of quantum theory were established, it was already noted that quantum physics may allow certain correlations defying any local realistic picture of nature, as first recognized by Einstein, Podolsky and Rosen. These quantum correlations, now termed quantum nonlocality and tested by violation of Bells inequality that consists of statistical correlations fulfilling local realism, have found loophole-free experimental confirmation. A more striking way to demonstrate the conflict exists, and can be extended to the multipartite scenario. Here we report experimental confirmation of such a striking way, the multipartite generalized Hardys paradoxes, in which no inequality is used and the conflict is stronger than that within just two parties. The paradoxes we are considering here belong to a general framework [S.-H. Jiang emph{et al.}, Phys. Rev. Lett. 120, 050403 (2018)], including previously known multipartite extensions of Hardys original paradox as special cases. The conflict shown here is stronger than in previous multipartite Hardys paradox. Thus, the demonstration of Hardy-typed quantum nonlocality becomes sharper than ever.
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Here we present the most general framework for $n$-particle Hardys paradoxes, which include Hardys original one and Cerecedas extension as special cases. Remarkably, for any $nge 3$ we demonstrate that there always exist generalized paradoxes (with t
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Characterizing high-dimensional entangled states is of crucial importance in quantum information science and technology. Recent theoretical progress has been made to extend the Hardys paradox into a general scenario with multisetting multidimensional
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Bells 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 $7sigma$. The fidelity of the GHZ state was around $81%$, and an entanglement witness reveals a violation of the separability threshold by $19sigma$.
Local realistic models cannot completely describe all predictions of quantum mechanics. This is known as Bells theorem that can be revealed either by violations of Bell inequality, or all-versus-nothing proof of nonlocality. Hardys paradox is an impo
rtant all-versus-nothing proof and is considered as the simplest form of Bells theorem. In this work, we theoretically build the general framework of Hardy-type paradox based on Bell inequality. Previous Hardys paradoxes have been found to be special cases within the framework. Stronger Hardy-type paradox has been found even for the two-qubit two-setting case, and the corresponding successful probability is about four times larger than the original one, thus providing a more friendly test for experiment. We also find that GHZ paradox can be viewed as a perfect Hardy-type paradox. Meanwhile, we experimentally test the stronger Hardy-type paradoxes in a two-qubit system. Within the experimental errors, the experimental results coincide with the theoretical predictions.
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