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We consider the violation of the Leggett-Garg inequality in electronic Mach-Zehnder inteferometers. This set-up has two distinct advantages over earlier quantum-transport proposals: firstly, the required correlation functions can be…

Mesoscale and Nanoscale Physics · Physics 2013-03-19 Clive Emary , Neill Lambert , Franco Nori

We derive a set of Leggett-Garg inequalities (temporal Bell's inequalities) for the moment generating function of charge transferred through a conductor. Violation of these inequalities demonstrates the absence of a macroscopic-real…

Mesoscale and Nanoscale Physics · Physics 2012-09-10 Clive Emary

In this paper, we study the two-time Leggett-Garg (LG) inequalities of a quantum optical model that appears in the Josephson-junction quantum bit (qubit) interacting with an external magnetic flux. This model is a natural extension of an…

Quantum Physics · Physics 2026-01-19 Hiroo Azuma

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

It is demonstrated that a weak measurement of the squared quadrature observable may yield negative values for coherent states. This result cannot be reproduced by a classical theory where quadratures are stochastic $c$-numbers. The real…

Quantum Physics · Physics 2009-11-10 Lars M. Johansen

Fluctuations of the work performed on a driven quantum system can be characterized by the so-called fluctuation theorems. The Jarzynski relation and the Crooks theorem are famous examples of exact equalities characterizing non-equilibrium…

Quantum Physics · Physics 2018-04-12 Alexey E. Rastegin

The violation of the Cauchy-Schwarz and Bell inequalities ranks among the major evidences of the genuinely quantum nature of an emitter. We show that by dispensing from the usual approximation of mode correlations and studying directly…

Quantum Physics · Physics 2015-06-19 Carlos Sánchez Muñoz , Elena del Valle , Carlos Tejedor , Fabrice P. Laussy

Standard Leggett and Garg inequalities (SLGIs) were formulated for testing the incompatibility between the classical worldview of macrorealism and quantum mechanics. In recent times, various other formulations, such as Wigner form of LGIs…

Quantum Physics · Physics 2017-10-17 Swati Kumari , A. K. Pan

Macro-realism is the position that certain "macroscopic" observables must always possess definite values: e.g. the table is in some definite position, even if we don't know what that is precisely. The traditional understanding is that by…

Quantum Physics · Physics 2017-07-17 John-Mark A. Allen , Owen J. E. Maroney , Stefano Gogioso

A recent paper by Souza, Oliveira and Sarthour (SOS) reports the experimental violation of a Leggett-Garg inequality (sometimes referred to as a temporal Bell inequality). The inequality tests for quantum mechanical superposition: if the…

Quantum Physics · Physics 2012-07-13 George C. Knee , Erik M. Gauger , G. Andrew D. Briggs , Simon C. Benjamin

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 study various formulations of Leggett-Garg inequality (LGI), specifically, the Wigner and Clauser-Horne forms of LGI, in the context of subatomic systems, in particular, three flavor neutrino as well as meson systems. The optimal forms…

High Energy Physics - Phenomenology · Physics 2020-08-04 Javid Naikoo , Swati Kumari , Subhashish Banerjee , A. K. Pan

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

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

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

Macrorealism is a belief that constitutes the core of our perception of reality in the everyday world. The Leggett-Garg (LG) test is a conceptually elegant approach for probing the compatibility between the notion of macrorealism and…

Quantum Physics · Physics 2023-11-09 A. K. Pan

We study some aspects of the Leggett-Garg inequalities by using the operator-state formalism for multitime processes. The process tensor in its Choi-state form, which we call process state, is employed to investigate the Leggett-Garg…

Quantum Physics · Physics 2025-06-12 Zhiqiang Huang , Xiao-Kan Guo

In quantum field theory, coherent states can be created that have negative energy density, meaning it is below that of empty space, the free quantum vacuum. If no restrictions existed regarding the concentration and permanence of negative…

Quantum Physics · Physics 2026-04-01 G. Jordan Maclay , Eric W. Davis

Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object --- in a dramatic scenario, a bomb --- without interacting with it. It was pointed out…

Quantum Physics · Physics 2017-02-01 Carsten Robens , Wolfgang Alt , Clive Emary , Dieter Meschede , Andrea Alberti

We analyze the continuous measurement of two non-commuting observables for a qubit, and investigate whether the simultaneously observed noisy signals are consistent with the evolution of an equivalent classical system. Following the…

Quantum Physics · Physics 2016-12-28 Luis Pedro García-Pintos , Justin Dressel
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