02.30.Bi Bell inequalities

Nonlocality in many-body quantum systems detected with two-body correlators

Date: 
2015-06-22 - 2015-07-24
Author(s): 

Jordi Tura, Remigiusz Augusiak, Ana Belén Sainz, Bernd Lücke, Carsten Klempt, Maciej Lewenstein, Antonio Acín

Reference: 

Annals of Physics, Volume 362, November 2015, Pages 370–423

Contemporary understanding of correlations in quantum many-body systems and in quantum phase transitions is based to a large extent on the recent intensive studies of entanglement in many-body systems.

Proposal to Test Bell’s Inequality in Electromechanics

Date: 
2016-06-03
Author(s): 

S. G. Hofer et al.

Reference: 

Phys. Rev. Lett. 116, 070406 (2016)

No Fine theorem for macrorealism: Limitations of the Leggett-Garg inequality

Date: 
2016-04-15
Author(s): 

L. Clemente and J Kofler

Reference: 

Phys. Rev. Lett. 116, 150401 (2016)

Violation of Bell inequalities in larger Hilbert spaces: robustness and challenges

Date: 
2016-01-08
Author(s): 

W. Weiss, G. Benenti, G. Casati, I. Guarneri, T. Calarco, M. Paternostro, S. Montangero

Reference: 

New J. Phys. 18 013021 (2016)
http://dx.doi.org/10.1088/1367-2630/18/1/013021

We explore the challenges posed by the violation of Bell-like inequalities by d-dimensional systems exposed to imperfect state-preparation and measurement settings. We address, in particular, the limit of high-dimensional systems, naturally arising when exploring the quantum-to-classical transition. We show that, although suitable Bell inequalities can be violated, in principle, for any dimension of given subsystems, it is in practice increasingly challenging to detect such violations, even if the system is prepared in a maximally entangled state.

Necessary and sufficient conditions for macroscopic realism from quantum mechanics

Date: 
2015-05-26
Author(s): 

L. Clemente and J. Kofler

Reference: 

arxiv:1501.07517

Macroscopic realism, the classical world view that macroscopic objects exist independently of and are not influenced by measurements, is usually tested using Leggett-Garg inequalities. Recently, another necessary condition called no-signaling in time (NSIT) has been proposed as a witness for non-classical behavior.

Linear optics schemes for entanglement distribution with realistic single-photon sources

Date: 
2014-09-22
Author(s): 

Mikołaj Lasota, Czesław Radzewicz, Konrad Banaszek, Rob Thew

Reference: 

Phys. Rev. A 90, 033836 (2014)

We study the operation of linear optics schemes for entanglement distribution based on nonlocal photon subtraction when input states, produced by imperfect single-photon sources, exhibit both vacuum and multiphoton contributions. Two models for realistic photon statistics with radically different properties of the multiphoton “tail” are considered. The first model assumes occasional emission of double photons and linear attenuation, while the second one is motivated by heralded sources utilizing spontaneous parametric down-conversion.

Challenging preconceptions about Bell tests with photon pairs

Date: 
2015-01-14
Author(s): 

V. Caprara Vivoli, P. Sekatski, J.-D. Bancal, C.C.W. Lim, B.G. Christensen, A. Martin, R.T. Thew, H. Zbinden, N. Gisin, N. Sangouard

Reference: 

Phys. Rev. A 91, 012107 (2015)

Motivated by very recent experiments, we consider a scenario "\`a la Bell" in which two protagonists test the Clauser-Horne-Shimony-Holt (CHSH) inequality using a photon-pair source based on spontaneous parametric down conversion and imperfect photon detectors.

Translationally invariant Bell inequalities with two-body correlators

Date: 
2013-12-01
Author(s): 

J. Tura, A. B. Sainz, T. Vértesi, A. Acín, M. Lewenstein, R. Augusiak

Reference: 

arXiv:1312.0265

Bell inequalities are natural tools that allow one to certify the presence of nonlocality in quantum systems. The known constructions of multipartite Bell inequalities contain, however, correlation functions involving all observers, making their experimental implementation difficult.

Bell inequalities with no quantum violation and unextendible product bases

Date: 
2011-08-12
Author(s): 

R. Augusiak, J. Stasinska, C. Hadley, J. K. Korbicz, M. Lewenstein, A. Acín

Reference: 

Phys. Rev. Lett. 107, 070401 (2011)

The strength of classical correlations is subject to certain constraints, commonly known as Bell inequalities. Violation of these inequalities is the manifestation of nonlocality---displayed, in particular, by quantum mechanics, meaning that quantum mechanics can outperform classical physics at tasks associated with such Bell inequalities. Interestingly, however, there exist situations in which this is not the case.

Fully nonlocal quantum correlations

Date: 
2012-03-05
Author(s): 

Leandro Aolita, Rodrigo Gallego, Antonio Acín, Andrea Chiuri, Giuseppe Vallone, Paolo Mataloni, Adán Cabello

Reference: 

Phys. Rev. A 85, 032107 (2012)

Quantum mechanics is a nonlocal theory, but not as nonlocal as the no-signalling principle allows. However, there exist quantum correlations that exhibit maximal nonlocality: they are as nonlocal as any nonsignalling correlation and thus have a local content, quantified by the fraction pL of events admitting a local description, equal to zero.

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