Experimental Violation of Local Realism by Four-Photon Greenberger-Horne-Zeilinger Entanglement

Zhao, Zhi; Yang, Tao; Chen, Yu-Ao; Zhang, Anning; Żukowski, Marek; Pan, Jian-Wei

doi:10.1103/physrevlett.91.180401

Cited by 210 publications

(121 citation statements)

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“…It should be emphasized that such a violation is predicted by quantum mechanics and appears when examining the data from the perspective of local realistic theories [6]. In addition, it should be stressed that the reported experiment is different as previous experiments to test local realism involving three or four-qubit GHZ states [13,14], since it is based on a definition of pairs which is conditioned to the result of a measurement on a third qubit, and requires performing measurements in additional configurations.…”

Section: Delaymentioning

confidence: 89%

Experimental Violation of Bell’s Inequality beyond Tsirelson’s Bound

et al. 2006

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The correlations between two qubits belonging to a three-qubit system can violate the ClauserHorne-Shimony-Holt-Bell inequality beyond Cirel'son's bound [A. Cabello, Phys. Rev. Lett. 88, 060403 (2002)]. We experimentally demonstrate such a violation by 7 standard deviations by using a three-photon polarization-entangled Greenberger-Horne-Zeilinger state produced by Type-II spontaneous parametric down-conversion. In addition, using part of our results, we obtain a violation of the Mermin inequality by 39 standard deviations.PACS numbers: 03.65. Ud, 03.67.Mn, 42.50.Dv, 42.50.Xa As stressed by Peres [1], Bell inequalities [2,3] have nothing to do with quantum mechanics. They are constraints imposed by local realistic theories on the values of linear combinations of the averages (or probabilities) of the results of experiments on two or more separated systems. Therefore, when examining data obtained in experiments to test Bell inequalities, it is legitimate to do it from the perspective (i.e., under the assumptions) of local realistic theories, without any reference to quantum mechanics. This approach leads to some apparently paradoxical results. A remarkable one is that, while it is a standard result in quantum mechanics that no quantum state can violate the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality [4] beyond Cirel'son's bound, namely 2 √ 2 [5], the correlations between two qubits belonging to a three-qubit system can violate the CHSHBell inequality beyond 2 √ 2 [6]. In particular, if we use a three-qubit Greenberger-Horne-Zeilinger (GHZ) state [7], we can even obtain the maximum allowed violation of the CHSH-Bell inequality, namely 4 [6].In this Letter, we report the first observation of a violation of the CHSH-Bell inequality beyond Cirel'son's bound by using a three-photon polarization-entangled GHZ state produced by Type-II spontaneous parametric down-conversion. In addition, since the experiment also provides all the data required for testing Mermin's threeparty Bell inequality [8], we use our results to demonstrate the violation of this inequality.The main idea behind the CHSH-Bell inequality [4] is that, in local realistic theories, the absolute value of a particular combination of correlations between two distant particles i and j is bounded by 2:where m and n can be either −1 or 1, and A and a (B and b) are physical observables taking values −1 or 1, referring to local experiments on particle i (j). The correlation C (A, B) of A and B is defined aswhere P AB (1, −1) denotes the joint probability of obtaining A = 1 and B = −1 when A and B are measured. Cirel'son proved that, for a two particle system prepared in any quantum state, the absolute value of the combination of quantum correlations appearing in the inequality (1) is bounded by 2 √ 2 [5]. However, assuming local realistic theories' point of view, the correlations predicted by quantum mechanics between two distant qubits belonging to a three-qubit system can violate the CHSHBell inequality beyond Cirel'son's bound [6].In our experiment,...

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Section: Delaymentioning

confidence: 89%

Experimental Violation of Bell’s Inequality beyond Tsirelson’s Bound

et al. 2006

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“…Such a violation is possible using quantum mechanical states with genuine tripartite entanglement (i.e. fully inseparable states), such as GHZ states of three qubits [15,16], up to…”

Section: Svetlichny Inequalitymentioning

confidence: 99%

“…Such an inequality can be violated e.g. by both Greenberger-Horne-Zeilinger (GHZ) and W classes of states for three qubits [15,16], and it stands as the conventional witness of genuine nonlocality when all three parties perform two measurements with two outcomes each [19], even though a large number of weaker inequalities revealing genuine nonlocality in more general settings have been constructed more recently [18,19]. While originally formulated for dichotomic observables, Bell-type inequalities such as the Svetlichny one can be tested for continuous variable systems either by binning outcomes of observables with continuous spectrum (typically Gaussianity-preserving measurements such as homodyne detection) [25,26], or by considering directly operators with a discrete spectrum [27,30].…”

Section: Introductionmentioning

confidence: 99%

“…While a great deal of attention has been devoted to the study of Bell inequalities in bipartite systems [1,3,4,6,7], including most recently the first loopholefree experimental demonstrations [8][9][10], a few criteria have been formulated for the verification of Bell nonlocality in multipartite systems as well [1,[11][12][13][14][15][16][17][18][19]. However, the concept of genuine multipartite nonlocality has been formalized only recently from an operational point of view [18,19] and its full exploration remains challenging both theoretically and experimentally.…”

Section: Introductionmentioning

confidence: 99%

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Genuine multipartite nonlocality of permutationally invariant Gaussian states

Tufarelli

Adesso

2017

Phys. Rev. A

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We investigate genuine multipartite nonlocality of pure permutationally invariant multimode Gaussian states of continuous variable systems, as detected by the violation of Svetlichny inequality. We identify the phase space settings leading to the largest violation of the inequality when using displaced parity measurements, distinguishing our results between the cases of even and odd total number of modes. We further consider pseudospin measurements and show that, for three-mode states with asymptotically large squeezing degree, particular settings of these measurements allow one to approach the maximum violation of Svetlichny inequality allowed by quantum mechanics. This indicates that the strongest manifestation of genuine multipartite quantum nonlocality is in principle verifiable on Gaussian states.

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“…Since the seminal work of Greenberger, Horne, and Zeilinger, the multiparticle maximally entangled states, known as GHZ states, has been receiving more and more attention [2]. They played a crucial role in fundamental tests of quantum mechanics versus local realism [42][43][44] and in new quantum information protocols [45]. As inspired by Bose et al [11], we generalize our hybrid entanglement swapping to three or more photon pairs, which provides a possible method to produce the OAM version of GHZ states.…”

Section: A a Creation Of Arbitrary Oam Bell States (N = 2)mentioning

confidence: 99%