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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

Wigner's form of the local realist inequality is used to derive its temporal version for an oscillating two-level system involving two-time joint probabilities. Such an inequality may be regarded as a novel form of the Leggett-Garg…

Quantum Physics · Physics 2015-03-24 Debashis Saha , Shiladitya Mal , Prasanta K. Panigrahi , Dipankar Home

Macroscopic realism (MR) is the view that a system may possess definite properties at any time independent of past or future measurements, and may be tested experimentally using the Leggett-Garg inequalities (LGIs). In this work we advance…

The Leggett-Garg (LG) inequalities were proposed in order to assess whether sets of pairs of sequential measurements on a single quantum system can be consistent with an underlying notion of macrorealism. Here, the LG inequalities are…

Quantum Physics · Physics 2016-03-02 J. J. Halliwell

Nonclassicality of temporal correlations pertaining to noncommutative sequential measurements is defined through the violation of macrorealistic inequalities, known as Leggett-Garg inequalities (LGI). We investigate the energy cost of the…

Quantum Physics · Physics 2018-09-11 Titas Chanda , Tamoghna Das , Shiladitya Mal , Aditi Sen De , Ujjwal Sen

Temporal Bell inequalities, or Leggett-Garg Inequalities (LGI), are studied for continuous-variable systems placed in a squeezed state. The importance of those systems lies in their broad applicability which allows the description of many…

Quantum Physics · Physics 2021-07-19 Jerome Martin , Vincent Vennin

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 and Garg Inequality (LGI) is a test of the classical behaviour of an observed system, in the case of a single measurement channel monitored at different times. Here we report LGI violation in cognitive tasks consisting in the…

Neurons and Cognition · Quantitative Biology 2013-05-27 F. T. Arecchi , A. Farini , N. Megna

In the Leggett-Garg approach to testing macrorealism, the two-time correlation functions, which are normally obtained by sequential measurements of a dichotomic variable Q, need to be measured in a non-invasive way in order to exclude…

Quantum Physics · Physics 2016-11-23 J. J. Halliwell

Macro-realistic description of systems is based majorly on two basic intuitions about the classical world, namely, macrorealism per se, that is, the system is always in a distinct state, and non-invasive measurements, that is, measurements…

Quantum Physics · Physics 2025-06-16 Shubhayan Sarkar

We show that the quantum bound for temporal correlations in a Leggett-Garg test, analogous to the Tsirelson bound for spatial correlations in a Bell test, strongly depends on the number of levels $N$ that can be accessed by the measurement…

Quantum Physics · Physics 2014-07-31 Costantino Budroni , Clive Emary

The Leggett-Garg inequality (LGI) is a temporal analogue of Bell's inequality and provides a quantitative test of the nonclassicality of a system through its violation. We analytically investigate the violation of the LGI in the context of…

General Relativity and Quantum Cosmology · Physics 2026-01-29 Kimihiro Nomura , Akira Taniguchi , Kazushige Ueda

The Leggett-Garg (LG) inequalities were introduced, as a temporal parallel of the Bell inequalities, to test macroscopic realism -- the view that a macroscopic system evolving in time possesses definite properties which can be determined…

Quantum Physics · Physics 2020-01-08 J. J. Halliwell

The Leggett-Garg inequality (LGI) places a bound for the distinction between quantum systems and classical systems. Despite that the tests of temporal quantum correlations on LGIs have been studied in Hermitian realm, there are still…

Quantum Physics · Physics 2024-06-21 Pengfei Lu , Xinxin Rao , Teng Liu , Yang Liu , Ji Bian , Feng Zhu , Le Luo

Characterization of quantum devices received from unknown providers is a significant primary task for any quantum information processing protocol. Self-testing protocols are designed for this purpose of certifying quantum components from…

Quantum Physics · Physics 2021-06-09 Ananda G. Maity , Shiladitya Mal , Chellasamy Jebarathinam , A. S. Majumdar

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

Contextuality means non-existence of a joint distribution for random variables recorded under mutually incompatible conditions, subject to certain constraints imposed on how the identity of these variables may change across these…

Quantum Physics · Physics 2015-02-06 Ehtibar N. Dzhafarov , Janne V. Kujala

Ambiguous measurements do not reveal complete information about the system under test. Their quantum-mechanical counterparts are semi-weak (or in the limit, weak-) measurements and here we discuss their role in tests of the Leggett-Garg…

Quantum Physics · Physics 2017-10-11 Clive Emary

It remains an open question how realist view of macroscopic world emerges from quantum formalism. For testing the macrorealism in quantum domain, an interesting approach was put forward by Leggett and Garg in $1985$, by formulating a…

Quantum Physics · Physics 2017-08-16 Swati Kumari , A. K. Pan

In contrast to Bell's inequalities which test the correlations between multiple spatially separated systems, the Leggett-Garg inequalities test the temporal correlations between measurements of a single system. We experimentally demonstrate…

Quantum Physics · Physics 2021-11-16 Wenlei Zhang , Ravi K. Saripalli , Jacob M. Leamer , Ryan T. Glasser , Denys I. Bondar
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