Probing the limits of correlations in an indivisible quantum system

Malinowski, Maciej; Zhang, Chi; Leupold, Florian; Cabello, Adán; Alonso, J.; Home, Jonathan

doi:10.1103/physreva.98.050102

Cited by 18 publications

(13 citation statements)

References 60 publications

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“…CbD is usually taken to be useful for inconsistently connected systems (systems with 'disturbance'), where measurements of the same property in different contexts may have differently distributed outcomes [5,[27][28][29][30][31]. However, if measurements are treated as random variables within the framework of classical probability theory, CbD offers considerable conceptual clarity even for consistently connected systems, those with no 'disturbance'.…”

Section: Introductionmentioning

confidence: 99%

On joint distributions, counterfactual values and hidden variables in understanding contextuality

Dzhafarov

2019

Phil. Trans. R. Soc. A.

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This paper deals with three traditional ways of defining contextuality: (C1) in terms of (non)existence of certain joint distributions involving measurements made in several mutually exclusive contexts; (C2) in terms of relationship between factual measurements in a given context and counterfactual measurements that could be made if one used other contexts; and (C3) in terms of (non)existence of "hidden variables" that determine the outcomes of all factually performed measurements. It is generally believed that the three meanings are equivalent, but the issues involved are not entirely transparent. Thus, arguments have been offered that C2 may have nothing to do with C1, and the traditional formulation of C1 itself encounters difficulties when measurement outcomes in a contextual system are treated as random variables. I show that if C1 is formulated within the framework of the Contextuality-by-Default (CbD) theory, the notion of a probabilistic coupling, the core mathematical tool of CbD, subsumes both counterfactual values and "hidden variables". In the latter case, a coupling itself can be viewed as a maximally parsimonious choice of a hidden variable.

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Section: Introductionmentioning

confidence: 99%

On joint distributions, counterfactual values and hidden variables in understanding contextuality

Dzhafarov

2019

Phil. Trans. R. Soc. A.

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“…The "maximally noncontextual models" [40,58] defined as those in which outcome noncontextuality holds with the maximum probability allowed by the observed marginals. That is, models that are only as conspiratorial as needed to account for the disturbance observed in the marginals.…”

Section: {I J}mentioning

confidence: 99%

Significant-loophole-free test of Kochen-Specker contextuality using two species of atomic-ions

Wang,

Zhang,

Luan

et al. 2021

Preprint

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Quantum measurements cannot be thought of as revealing preexisting results, even when they do not disturb any other measurement in the same trial. This feature is called contextuality and is crucial for the quantum advantage in computing. Here, we report the first observation of quantum contextuality simultaneously free of the detection, sharpness and compatibility loopholes. The detection and sharpness loopholes are closed by adopting a hybrid two-ion system and highly efficient fluorescence measurements offering a detection efficiency of 100% and a measurement repeatability > 98%. The compatibility loophole is closed by targeting correlations between observables for two different ions in a Paul trap, a 171 Yb + ion and a 138 Ba + ion, chosen so measurements on each ion use different operation laser wavelengths, fluorescence wavelengths, and detectors. The experimental results show a violation of the bound for the most adversarial noncontextual models and open a new way to certify quantum systems.

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“…However, as tests of noncontextual models, they leave open the sharpness loophole. On the other hand, there are contextuality tests free of the detection loophole and whose correlations cannot be produced by specific mechanisms exploiting the lack of perfect repeatability ( 19 , 40 ). However, they suffer from the compatibility loophole, as they require sequential measurements performed on the same system.…”

Section: Introductionmentioning

confidence: 99%

Significant loophole-free test of Kochen-Specker contextuality using two species of atomic ions

et al. 2022

View full text Add to dashboard Cite

Quantum measurements cannot be thought of as revealing preexisting results, even when they do not disturb any other measurement in the same trial. This feature is called contextuality and is crucial for the quantum advantage in computing. Here, we report the observation of quantum contextuality simultaneously free of the detection, sharpness, and compatibility loopholes. The detection and sharpness loopholes are closed by adopting a hybrid two-ion system and highly efficient fluorescence measurements offering a detection efficiency of 100% and a measurement repeatability of >98%. The compatibility loophole is closed by targeting correlations between observables for two different ions in a Paul trap, a 171 Yb + ion and a 138 Ba + ion, chosen so measurements on each ion use different operation laser wavelengths, fluorescence wavelengths, and detectors. The experimental results show a violation of the bound for the most adversarial noncontextual models and open a way to certify quantum systems.

show abstract

Probing the limits of correlations in an indivisible quantum system

Cited by 18 publications

References 60 publications

On joint distributions, counterfactual values and hidden variables in understanding contextuality

On joint distributions, counterfactual values and hidden variables in understanding contextuality

Significant-loophole-free test of Kochen-Specker contextuality using two species of atomic-ions

Significant loophole-free test of Kochen-Specker contextuality using two species of atomic ions

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