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Generalised quantum measurements with two outcomes are fully characterised by two real parameters, dubbed as sharpness parameter and biasedness parameter and they can be linked with different aspects of the experimental setup. It is known…

Quantum Physics · Physics 2018-04-04 Debarshi Das , Shiladitya Mal , Dipankar Home

We report on an experiment that demonstrates the violation of a Leggett-Garg inequality (LGI) with neutrons. LGIs have been proposed in order to assess how far the predictions of quantum mechanics defy macroscopic realism. With LGIs,…

Quantum Physics · Physics 2024-07-08 Elisabeth Kreuzgruber , Richard Wagner , Niels Geerits , Hartmut Lemmel , Stephan Sponar

In this work, we deal with the relaxation of two central assumptions in standard locally realistic hidden variable (LRHV) inequalities: free will in choosing measurement settings, and the presence of perfect detectors at the measurement…

Quantum Physics · Physics 2023-02-07 Abhishek Sadhu , Siddhartha Das

The possibility of observing violations of temporal Bell inequalities, originally proposed by Leggett as a mean of testing the quantum mechanical delocalization of suitably chosen macroscopic bodies, is discussed by taking into account the…

Quantum Physics · Physics 2009-10-31 Tommaso Calarco , Marcello Cini , Roberto Onofrio

The quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test…

In this study, we determine a violation of the Leggett-Garg inequalities due to gravitational interaction in a hybrid system consisting of a harmonic oscillator and a spatially localized superposed particle. The violation of the…

Quantum Physics · Physics 2022-08-23 Akira Matsumura , Yasusada Nambu , Kazuhiro Yamamoto

We show how one may test macroscopic local realism where, different from conventional Bell tests, all relevant measurements need only distinguish between two macroscopically distinct states of the system being measured. Here, measurements…

Quantum Physics · Physics 2024-12-13 M. Thenabadu , G-L. Cheng , T. L. H. Pham , L. V. Drummond , L. Rosales-Zárate , M. D. Reid

Quantum mechanics has always proven emphatically as one of the main cornerstones in all of science since its inception. Initially, it has also faced many skeptics from many scientific proponents of its complete description of reality.…

High Energy Physics - Phenomenology · Physics 2024-10-30 Kiran Sharma , Aryabrat Mahapatra , Prasanta K. Panigrahi , Sudhanwa Patra

Demonstrating contextual correlations in quantum theory through the violation of a non-contextuality inequality necessarily needs some ``contexts" and thus assumes some compatibility relations between the measurements. As a result, any…

Quantum Physics · Physics 2024-12-03 Gautam Sharma , Chellasamy Jebarathinam , Sk Sazim , Remigiusz Augusiak

Model-checking techniques have been extended to analyze quantum programs and communication protocols represented as quantum Markov chains, an extension of classical Markov chains. To specify qualitative temporal properties, a subspace-based…

Quantum Physics · Physics 2024-05-10 Ji Guan , Yuan Feng , Andrea Turrini , Mingsheng Ying

The Leggett-Garg Inequality (LGI) constrains, under certain fundamental assumptions, the correlations between measurements of a quantity Q at different times. Here we analyze the LGI, and propose similar but somewhat more elaborate…

Quantum Physics · Physics 2023-04-21 Dana Ben Porath , Eliahu Cohen

The Leggett-Garg inequalities impose restrictions on the values taken by some combinations of the two-time correlation functions of observables in order to be explainable by a noninvasive-realist classical model. While in the unitary…

Quantum Physics · Physics 2021-01-19 Javid Naikoo , Subhashish Banerjee , R. Srikanth

We generalize the derivation of Leggett-Garg inequalities to systematically treat a larger class of experimental situations by allowing multi-particle correlations, invasive detection, and ambiguous detector results. Furthermore, we show…

Quantum Physics · Physics 2015-03-18 J. Dressel , C. J. Broadbent , J. C. Howell , A. N. Jordan

We apply the Leggett-Garg inequalities (LGI) to the case of classical and quantum unstable systems. For classical systems the two assumptions of macroscopic realism and non-invasive measurements imply that the three-measurement string $K_3$…

Quantum Physics · Physics 2021-12-08 Francesco Giacosa , Giuseppe Pagliara

The Leggett-Garg inequality (LGI) distinguishes nonmacrorealistic channels from macrorealistic ones by constraining the experimental outcomes of the underlying system. In this work, we propose a class of channels which, initially, cannot…

In this, partly pedagogical review, I attempt to give a self-contained overview of the basis of (non-relativistic) QM measurement theory expressed in density matrix formalism. The focus is on applications to the theory of weak measurement,…

Quantum Physics · Physics 2013-05-27 Bengt E. Y. Svensson

Leggett-type nonlocal realist inequalities that have been derived to date are all contingent upon suitable geometrical constraints to be strictly satisfied by the spatial arrangement of the relevant measurement settings. This undesirable…

Quantum Physics · Physics 2015-03-19 Ashutosh Rai , Dipankar Home , A. S. Majumdar

We consider maximal violations of the Leggett-Garg inequality, obtained by maximising over all possible measurement operators, in relation to non-unitary aspects of the system dynamics. We model the action of an environment on a qubit in…

Quantum Physics · Physics 2013-04-22 Clive Emary

We establish an objective scheme to determine the macroscopicity of quantum mechanical superposition tests, which is based on the Bayesian hypothesis falsification of macrorealistic modifications of quantum theory. The measure uses the raw…

Quantum Physics · Physics 2019-10-01 Björn Schrinski , Stefan Nimmrichter , Benjamin A. Stickler , Klaus Hornberger

We investigate the nonclassicality of an open quantum system using Leggett-Garg inequality (LGI) which test the correlations of a single system measured at different times. Violation of LGI implies nonclassical behavior of the open system.…

Quantum Physics · Physics 2017-04-11 Md. Manirul Ali , Po-Wen Chen