We present a simple analytic bound on the quantum value of general correlation type Bell inequalities, similar to Tsirelson's bound. It is based on the maximal singular value of the coefficient matrix associated with the inequality. We provide a criterion for tightness of the bound and show that the class of inequalities where our bound is tight covers many famous examples from the literature. We describe how this bound helps to construct Bell inequalities, in particular inequalities that witness the dimension of the measured observables.
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http://dx.doi.org/10.1103/PhysRevLett.111.240404 | DOI Listing |
Entropy (Basel)
December 2024
Joint Laboratory of Optics of Palacký University and Institute of Physics of AS CR, Faculty of Science, Palacký University, 17. listopadu 12, 779 00 Olomouc, Czech Republic.
We discuss a family of W-class states describing three-qubit systems. For such systems, we analyze the relations between the entanglement measures and the nonlocality parameter for a two-mode mixed state related to the two-qubit subsystem. We find the conditions determining the boundary values of the negativity, parameterized by concurrence, for violating the Bell-CHSH inequality.
View Article and Find Full Text PDFPhilos Trans A Math Phys Eng Sci
December 2024
Max-Planck-Institut für die Physik des Lichts, Staudtstraße 2, Erlangen 91058, Germany.
Quantum entanglement describes superposition states in multi-dimensional systems-at least two partite-which cannot be factorized and are thus non-separable. Non-separable states also exist in classical theories involving vector spaces. In both cases, it is possible to violate a Bell-like inequality.
View Article and Find Full Text PDFEPJ Quantum Technol
December 2024
Departament de Física Quàntica i Astrofísica, Facultat de Física, Universitat de Barcelona (UB), C. Martí i Franquès, 1, 08028 Barcelona, Spain.
The growth of quantum technologies is attracting the interest of many students eager to learn concepts such as quantum entanglement or quantum superposition. However, the non-intuitive nature of these concepts poses a challenge to understanding them. Here, we present an entangled photon system which can perform a Bell test, i.
View Article and Find Full Text PDFFundam Res
July 2024
College of Electronic and Optical Engineering, & College of Flexible Electronics (Future Technology), Nanjing University of Posts and Telecommunications, Nanjing 210023, China.
Quantum secure direct communication (QSDC) can directly transmit secret messages through quantum channel without keys. Device-independent (DI) QSDC guarantees the message security relying only on the observation of the Bell-inequality violation, but not on any detailed description or trust of the devices' inner workings. Compared with conventional QSDC, DI-QSDC has relatively low secret message capacity.
View Article and Find Full Text PDFPLOS Glob Public Health
December 2024
Kirby Institute, UNSW Sydney, Sydney, Australia.
Unintended adolescent pregnancy is a public health priority in Papua New Guinea (PNG), where national policies specify need for easier access to reliable modern contraceptives. To reduce young people's experiences of unintended pregnancy in PNG, improved understandings of use of modern and other forms of contraception within young people's relationships is required to support the development of new sexual and reproductive health (SRH) programs and policies. The aim of this paper is to understand young men's use of modern and other contraceptives.
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