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In an endeavour to better define the distinction between classical macroscopic and quantum microscopic regimes, the Leggett-Garg inequalities were established as a test of macroscopic-realistic theories, which are commonly thought to be a…

Quantum Physics · Physics 2021-04-14 Hadrien Chevalier , A. J. Paige , Hyukjoon Kwon , M. S. Kim

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

We discuss a scheme for macrorealistic theories of the Leggett-Garg form [A. J. Leggett and A. Garg, Phys. Rev. Lett. 54, 857 (1985)]. Our scheme is based on a hybrid optomechanical system. It seems reasonable to test these inequalities…

Quantum Physics · Physics 2020-03-13 Marta Maria Marchese , Hannah McAleese , Angelo Bassi , Mauro Paternostro

We investigate the Leggett-Garg inequalities (LGIs) for a boson system whose observables are given by deforming the Pegg-Barnett phase operators. We consider two observables and show that the quantum Fourier transform is useful in the…

Quantum Physics · Physics 2023-02-09 Hiroo Azuma , William J. Munro , Kae Nemoto

In 1985, Leggett and Garg formulated a class of inequalities for testing the compatibility between macrorealism and quantum mechanics. In this paper, we point out that based on the same assumptions of macrorealism that are used in the…

Quantum Physics · Physics 2020-12-29 A. K. Pan , Md. Qutubuddin , Swati Kumari

The Leggett-Garg inequalities are a set of inequalities obeyed by classical systems but violated in quantum theory. Their violation has been taken as evidence that quantum theory lacks a `realistic' formulation. However in addition to…

Quantum Physics · Physics 2013-10-09 JM Yearsley

The correlations between successive measurements of a quantum system can violate a family of Leggett-Garg Inequalities (LGIs) that are analogous to the violation of Bell's inequalities of measurements performed on spatially separated…

High Energy Physics - Phenomenology · Physics 2026-01-30 Kathrine Mørch Groth , Johann Ioannou-Nikolaides , D. Jason Koskinen , Markus Ahlers

The Bell and Leggett-Garg tests offer operational ways to demonstrate that non-classical behavior manifests itself in quantum systems, and experimentalists have implemented these protocols to show that classical worldviews such as local…

Quantum Physics · Physics 2010-09-24 David Avis , Patrick Hayden , Mark M. Wilde

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

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

We show how to apply the Leggett-Garg inequality to opto-electro-mechanical systems near their quantum ground state. We find that by using a dichotomic quantum non-demolition measurement (via, e.g., an additional circuit-QED measurement…

Quantum Physics · Physics 2012-09-17 Neill Lambert , Robert Johansson , Franco Nori

Macrorealism formalizes the intuitive notion that at any given time the system occupies a definite state and that the evolution of the system is independent of the measurements performed on it, in contrast to the principles of quantum…

We describe a new and experimentally feasible protocol for performing fundamental tests of quantum mechanics with massive objects. In our approach a single two level system is used to probe the motion of a nanomechanical resonator via…

Quantum Physics · Physics 2014-05-20 A. Asadian , C. Brukner , P. Rabl

Leggett Garg inequalities (LGIs) test the incompatibility between the notion of macrorealism and quantum mechanics. For unitary dynamics, the optimal quantum violation of an LGI is constrained by the L\"uders bound. However, the LGIs does…

Quantum Physics · Physics 2022-05-18 Asmita Kumari , A. K. Pan

"Macrorealism" posits that a system possesses definite properties at all times and that we can discover these properties, in principle, without disturbing the system's subsequent behaviour. The Leggett-Garg inequalities are derived under…

Quantum Physics · Physics 2026-05-22 Arush Garg , Jonathan Halliwell , Taejas Venkataraman

We investigate violations of Leggett-Garg inequalities (LGIs) for a harmonic oscillator and a (1+1)-dimensional chiral scalar field with coherent-state projectors, which is equivalent to a heterodyne-type measurement scheme. For the…

Quantum Physics · Physics 2024-01-30 Tomoya Hirotani , Akira Matsumura , Yasusada Nambu , Kazuhiro Yamamoto

The Leggett-Garg inequality attempts to classify experimental outcomes as arising from one of two possible classes of physical theories: those described by macrorealism (which obey our intuition about how the macroscopic classical world…

Quantum Physics · Physics 2020-12-22 Huan-Yu Ku , Neill Lambert , Fong-Ruei Jhan , Clive Emary , Yueh-Nan Chen , Franco Nori

Leggett-Garg Inequality~(LGI) is a time analogue of Bell's inequality that concerns measurements performed on a system at different times. Violation to LGI indicates quantum coherence. We present a Leggett-Garg-type inequality compatible…

Quantum Physics · Physics 2022-02-15 Xing-Zhi Wang , Bo-Qiang Ma

We interpret the Leggett-Garg (LG) inequality as a kind of contextual probabilistic inequality in which one combines data collected in experiments performed for three different contexts. In the original version of the inequality these…

Neurons and Cognition · Quantitative Biology 2015-06-18 Masanari Asano , Takahisa Hashimoto , Andrei Khrennikov , Masanori Ohya , Yoshiharu Tanaka

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