A weak values approach for testing simultaneous Einstein–Podolsky–Rosen elements of reality for non-commuting observables

Calderón-Losada, Omar; Quistian, Tonatiuh T. Moctezuma; Cruz-Ramírez, Héctor; Ramírez, Sebastián Murgueitio; U’Ren, Alfred B.; Botero, Alonso; Valencia, Alejandra

doi:10.1038/s42005-020-0378-3

Cited by 7 publications

(2 citation statements)

References 29 publications

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“…Weak measurements have already represented a tool for quantum foundations experiments, e.g. in connection with quantum contextuality [21][22][23], nonlocality [24,25], Leggett-Garg inequalities [26,27] and the Einstein-Podolski-Rosen paradox [28]. Our result represents a breakthrough application of them, since, for the first time, they allow evaluating the entire Bell parameter individually from each entangled pair detected (although with a large uncertainty, typical of weak measurements).…”

Section: Introductionmentioning

confidence: 76%

Single-pair measurement of the Bell parameter

Virzì¹,

Rebufello²,

Atzori³

et al. 2023

Preprint

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Bell inequalities are one of the cornerstones of quantum foundations and fundamental tools for quantum technologies. Recently, the scientific community worldwide has put a lot of effort towards them, which culminated with loophole-free experiments. Nonetheless, none of the experimental tests so far was able to extract information on the full inequality from each entangled pair, since the wave function collapse forbids performing, on the same quantum state, all the measurements needed for evaluating the entire Bell parameter. We present here the first single-pair Bell inequality test, able to obtain a Bell parameter value for every entangled pair detected. This is made possible by exploiting sequential weak measurements, allowing to measure non-commuting observables in sequence on the same state, on each entangled particle. Such an approach not only grants unprecedented measurement capability, but also removes the need to choose between different measurement bases, intrinsically eliminating the freedom-of-choice loophole and stretching the concept of counterfactual-definiteness, since it allows measuring in the otherwise not-chosen bases. We also demonstrate how, after the Bell parameter measurement, the pair under test still presents a noteworthy amount of entanglement, providing evidence of the absence of (complete) wave function collapse and allowing to exploit this quantum resource for further protocols.

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Section: Introductionmentioning

confidence: 76%

Single-pair measurement of the Bell parameter

Virzì¹,

Rebufello²,

Atzori³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…It is then possible to reconstruct quasi-probabilities for the input state, resulting in an explanation of Bell's inequality violations by negative values in the reconstructed probability distribution [28]. Weak measurements have also been used to demonstrate the correspondence of weak values with the "elements of reality" of the EPR paradox [34]. However, the highly biased distribution of measurement uncertainties means that the relation between the non-commuting observables appears in a somewhat distorted manner in the raw data.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of the relation between measurement uncertainties and non-local quantum correlations

Matsuyama,

Hofmann,

Iinuma

2021

Preprint

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Bell's inequalities are defined by sums of correlations involving noncommuting observables in each of the two systems. Violations of Bell's inequalities are only possible because the precision of any joint measurement of these observables will be limited by quantum mechanical uncertainty relations. In this paper we explore the relation between the local measurement uncertainties and the magnitude of the correlations by preparing polarization entangled photon pairs and performing joint measurements of non-commuting polarization components at different uncertainty trade-offs. The change in measurement visibility reveals the existence of a non-trivial balance between the measurement uncertainties where the probabilities of a specific pair of measurement outcomes approaches zero because of the particular combination of enhancement and suppression of the experimentally observed correlations. The occurrence of these high-contrast results shows that the quantum correlations between the photons are close to their maximal value, confirming that the Cirel'son bound of Bell's inequality violations is defined by the minimal uncertainties that limit the precision of joint measurements.

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Entanglement-preserving measurement of the Bell parameter on a single entangled pair

Virzì,

Rebufello,

Atzori

et al. 2024

Quantum Sci. Technol.

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Bell inequalities represent one of the cornerstones of quantum foundations, and a fundamental tool for quantum technologies.Although a lot of effort was put in exploring and generalizing them, because of the wave function collapse it was deemed impossible to estimate the entire Bell parameter from one entangled pair, since this would involve measuring incompatible observables on the same quantum state.Conversely, here it is reported the first implementation of a new generation of Bell inequality tests, able to extract a Bell parameter value from each entangled pair and, at the same time, preserve the pair entanglement instead of destroying it.This is obtained by exploiting sequences of weak measurements, allowing incompatible observable measurements on a quantum state without collapsing its wave function.On the fundamental side, by removing the need to choose between different measurement bases our approach stretches the concept of counterfactual definiteness, since it allows measuring the entangled pair in all the bases needed for the Bell inequality test, intrinsically eliminating the issues connected with the otherwise not-chosen bases.On the practical side, after our Bell parameter measurement the entanglement within the pair remains (basically) unaltered, hence exploitable for other quantum-technology-related or foundational purposes.

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A weak values approach for testing simultaneous Einstein–Podolsky–Rosen elements of reality for non-commuting observables

Cited by 7 publications

References 29 publications

Single-pair measurement of the Bell parameter

Single-pair measurement of the Bell parameter

Experimental investigation of the relation between measurement uncertainties and non-local quantum correlations

Entanglement-preserving measurement of the Bell parameter on a single entangled pair

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