Article
Astronomy & Astrophysics
S. P. Sorella
Summary: We discuss the relationship between Bogoliubov transformations, squeezed states, entanglement, and the maximum violation of the Bell-CHSH inequality. We point out a simple and general method to construct the bounded operators involved in the Bell-CHSH inequality, which is applicable to a wide range of models from quantum mechanics to relativistic quantum field theories. Various examples are provided to illustrate this framework, including entangled spin-one particles, squeezed oscillators, and the vacuum state in Minkowski spacetime parametrized by the Unruh temperature.
Article
Astronomy & Astrophysics
G. Peruzzo, S. P. Sorella
Summary: This study investigates the Clauser-Horne-Shimony-Holt (CHSH) inequality within a relativistic quantum field theory model. A set of bounded Hermitian operators is introduced using Weyl operators, and a CHSH-type correlator is constructed and evaluated. Although the violation of the CHSH inequality is small compared to Tsirelson's bound in quantum mechanics, the model can be used to study Bell's inequalities in more physical cases such as the Higgs models.
Article
Astronomy & Astrophysics
G. Peruzzo, S. P. Sorella
Summary: By employing a free scalar quantum field theory model introduced previously, the authors attempt to formulate the Bell-CHSH inequality within the Feynman path integral. They observe that the Bell-CHSH inequality naturally extends to quantum field theory and is compatible with the time ordering T. By treating the Feynman propagator as a distribution and introducing a suitable set of test functions, they work out the path integral setup for the Bell-CHSH inequality, obtaining the same results as canonical quantization.
Article
Physics, Applied
Xin Tong, Zhe He, Yide Zhang, Samuel Solomon, Li Lin, Qiyuan Song, Lihong V. Wang
Summary: Experimental measurement of quantum correlation is used to establish nonlocality and entanglement inequalities, which are employed to test nonclassical correlations. The correlation maps are applied in an entanglement-based quantum key distribution protocol.
PHYSICAL REVIEW APPLIED
(2023)
Article
Quantum Science & Technology
J. Cortes-Vega, J. F. Barra, L. Pereira, A. Delgado
Summary: In this study, a method is proposed to detect the entanglement of unknown two-qubit quantum states. The method is based on the violation of the Clauser-Horne-Shimony-Holt inequality. Numerical simulations demonstrate that the algorithm surpasses the classical limit after a few iterations.
QUANTUM INFORMATION PROCESSING
(2023)
Article
Astronomy & Astrophysics
P. De Fabritiis, F. M. Guedes, M. S. Guimaraes, G. Peruzzo, I. Roditi, S. P. Sorella
Summary: The violation of the Bell-Clauser-Horne-Shimony-Holt inequality in the vacuum state of a relativistic free real scalar field is demonstrated through the direct computation of the correlation functions of Weyl operators using the Tomita-Takesaki construction.
Article
Optics
Ricardo Faleiro, Manuel Goulao
Summary: In this study, a two-party quantum authorization primitive fueled by nonlocality is proposed. Users are granted access to a private database based on their authorization levels encoded in nonlocal resources, confirmed through winning games. The protocol is formalized, proven secure, and framed in a device-independent setting, with a proof-of-concept implementation using the QISKIT open-source framework.
Article
Astronomy & Astrophysics
David Dudal, Philipe De Fabritiis, Marcelo S. Guimaraes, Itzhak Roditi, Silvio P. Sorella
Summary: In this paper, we propose a general setup to investigate the violation of the Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) inequality in the vacuum state in the context of quantum field theory. By constructing specific test functions and satisfying relativistic causality requirements, we report violations of the Bell-CHSH inequality as close as desired to Tsirelson's bound.
Article
Optics
Johannes Seiler, Thomas Strohm, Wolfgang P. Schleich
Summary: The study reveals that maximizing the correlation measure in the Clauser-Horne-Shimony-Holt inequality for pure and mixed states can be simplified to maximizing the perimeter of a parallelogram enclosed by an ellipse characterized by the entanglement in the bipartite system. This geometrical description is applicable to nonmaximally entangled states, and the corresponding optimal measurements have been identified.
Article
Optics
Johannes Seiler, Thomas Strohm, Wolfgang P. Schleich
Summary: This research demonstrates the equivalence between the Hardy nonlocality condition and the violation of the CHSH inequality alongside additional constraints. By adapting the geometrical optimization approach, the study reveals that the Hardy condition can be represented as optimizing the length difference between two sides of a triangle. Moreover, the effects of different constraints are discussed.
Article
Physics, Multidisciplinary
Xavier Valcarce, Julian Zivy, Nicolas Sangouard, Pavel Sekatski
Summary: Device-independent certification, also known as self-testing, aims to ensure the proper functioning of untrusted and uncharacterized devices. This paper demonstrates an improved self-testing approach for two-qubit maximally entangled states through a refined analysis of measurement statistics. By using suitably chosen Bell tests and observing correlations, higher fidelities can be concluded than previously known, even from correlations that cannot be exploited by a CHSH-based self-testing strategy.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Optics
Antoni Mikos-Nuszkiewicz, Jedrzej Kaniewski
Summary: Quantum mechanics has the potential to revolutionize modern information processing in various fields including cryptography, computing, and metrology. Quantum cryptography enables device-independent protocols with proven security. Analytical families of quantum extremal points are introduced in this study, along with an analysis of extremality criteria in the CHSH scenario. A set of conditions is proposed based on the technical details and physical interpretation, and its predictions on quantum extremal points are verified.
Article
Optics
Shuo Wang, Ya Xiao, Xin-Hong Han, Xuan Fan, Tian Qian, Yong-Jian Gu
Summary: This study proposes a generalized entanglement-assisted communication complexity reduction protocol and analyzes its quantum superiority against measurement imperfections. It is found that quantum superiority can be achieved in specific entangled states within a certain range of measurement parameters, and it strengthens with an increase in entanglement degree.
Article
Mathematics, Applied
Jian-Feng Cai, Meng Huang, Dong Li, Yang Wang
Summary: The phase retrieval problem involves recovering an unknown signal x from magnitude-only measurements. A natural least squares formulation can efficiently solve this problem, even with random initialization, despite the non-convexity of the loss function. The paper shows that m = O(n log n) Gaussian random measurements are sufficient to ensure the favorable geometric property of a commonly used estimator with high probability, progressing towards answering an open problem in the field.
Article
Mathematics, Applied
Bianca Gariboldi, Giacomo Gigante
Summary: The text discusses the extension of the theorem regarding L-designs by A. Bondarenko, D. Radchenko and M. Viazovska to d-dimensional compact connected oriented Riemannian manifolds. To prove this theorem, a version of the Marcinkiewicz-Zygmund inequality for the gradient of diffusion polynomials needs to be established.
Article
Physics, Multidisciplinary
Marc Olivier Renou, Jedrzej Kaniewski, Nicolas Brunner
PHYSICAL REVIEW LETTERS
(2018)
Article
Physics, Multidisciplinary
Sebastien Designolle, Mate Farkas, Jedrzej Kaniewski
NEW JOURNAL OF PHYSICS
(2019)
Article
Multidisciplinary Sciences
Armin Tavakoli, Mate Farkas, Denis Rosset, Jean-Daniel Bancal, Jedrzej Kaniewski
Summary: The text discusses the importance of mutually unbiased bases (MUBs) and symmetric informationally complete projectors (SICs) in quantum theory, particularly in the context of quantum nonlocality. It highlights the development of Bell inequalities, device-independent certification, and protocols for quantum key distribution and quantum random number generation using MUBs and SICs. Additionally, it presents the first example of an extremal point in the quantum set of correlations with physically inequivalent quantum realizations.
Article
Quantum Science & Technology
Shubhayan Sarkar, Debashis Saha, Jedrzej Kaniewski, Remigiusz Augusiak
Summary: Bell nonlocality as a resource for device-independent certification schemes has been extensively studied, and a self-testing protocol for the maximally entangled state of any local dimension using the minimum number of measurements possible has been proposed, which can achieve unbounded randomness expansion and log 2d perfect random bits with only one random bit required for encoding measurement choice.
NPJ QUANTUM INFORMATION
(2021)
Article
Physics, Multidisciplinary
Krzysztof Mordasewicz, Jedrzej Kaniewski
Summary: The existence of incompatible measurements is an important distinction between quantum mechanics and classical theories, but it is also a necessary ingredient for achieving quantum advantage. To quantify incompatibility, a family of incompatibility measures based on non-commutativity is defined and explored. The basic properties of these measures are investigated, and the pairs achieving the highest incompatibility are fully characterized.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2022)
Article
Optics
Gabriel Pereira Alves, Jedrzej Kaniewski
Summary: Bell nonlocality is a significant departure of quantum mechanics from classical physics, showing that quantum correlations between spacelike separated systems are stronger than classical correlations. A recent study proposed a family of Bell functionals tailored to mutually unbiased bases (MUBs) and generalized it to an arbitrary incompatible pair of rank-one projective measurements. They demonstrated that there exists a Bell inequality that is maximally violated by any such pair of measurements and showed that the most noise-resilient realization is not generated by MUBs.
Article
Physics, Multidisciplinary
Erik Woodhead, Jedrzej Kaniewski, Boris Bourdoncle, Alexia Salavrakos, Joseph Bowles, Antonio Acin, Remigiusz Augusiak
PHYSICAL REVIEW RESEARCH
(2020)
Article
Physics, Multidisciplinary
Jedrzej Kaniewski
PHYSICAL REVIEW RESEARCH
(2020)
Article
Quantum Science & Technology
Jedrzej Kaniewski, Ivan Supic, Jordi Tura, Flavio Baccari, Alexia Salavrakos, Remigiusz Augusiak
Article
Optics
Tim Coopmans, Jedrzej Kaniewski, Christian Schaffner
Article
Optics
Mate Farkas, Jedrzej Kaniewski
Article
Optics
Armin Tavakoli, Jedrzej Kaniewski, Tamas Vertesi, Denis Rosset, Nicolas Brunner
Article
Optics
Jeremy Ribeiro, Le Phuc Thinh, Jedrzej Kaniewski, Jonas Helsen, Stephanie Wehner
Article
Optics
Koon Tong Goh, Jedrzej Kaniewski, Elie Wolfe, Tamas Vertesi, Xingyao Wu, Yu Cai, Yeong-Cherng Liang, Valerio Scarani
Article
Optics
Jedrzej Kaniewski