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Quantum theory contravenes classical macrorealism by allowing a system to be in a superposition of two or more physically distinct states, producing physical consequences radically different from that of classical physics. We show that a…

Quantum Physics · Physics 2026-02-03 Arijit Chatterjee , H. S. Karthik , T. S. Mahesh , A. R. Usha Devi

Evolution time of a qubit under a Hamiltonian operation is one of the key issues in quantum control, quantum information processing and quantum computing. It has a lower bound in Hermitian system, which is limited by the coupling between…

Atomic Physics · Physics 2022-06-03 Pengfei Lu , Teng liu , Yang Liu , Xinxin Rao , Qifeng Lao , Hao Wu , Feng Zhu , Le Luo

Although coherent manipulation of electronic states can be achieved in quantum dot (QD) devices by harnessing nanofabrication tools, it is often hard to fathom the extent to which these nanoelectronic devices can behave quantum…

Quantum Physics · Physics 2024-10-25 Thingujam Yaiphalemba Meitei , Saikumar Krithivasan , Arijit Sen , Md Manirul Ali

Leggett-Garg inequality (LGI) studies the temporal correlation in the evolution of physical systems. Classical systems obey the LGI but quantum systems may violate it. The extent of the violation depends on the dimension of the quantum…

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

We show violations of Leggett-Garg inequalities to be possible for single-mode cat-states evolving dynamically in the presence of a nonlinear quantum interaction arising from, for instance, a Kerr medium. In order to prove the results, we…

Quantum Physics · Physics 2019-04-03 Manushan Thenabadu , Margaret Reid

The requirement for Hermiticity in quantum mechanics ensures the reality of energies, while the parity-time symmetry offers an alternative route to achieve this goal. Interestingly, in a three-level system, the parity-time symmetry-breaking…

Quantum Physics · Physics 2025-12-05 Y. -Y. Chen , K. Li , L. Zhang , Y. -K. Wu , J. -Y. Ma , H. -X. Yang , C. Zhang , B. -X. Qi , Z. -C. Zhou , P. -Y. Hou , Y. Xu , L. -M. Duan

We investigate Leggett-Garg temporal inequalities in flavor-mixing processes. We derive an exact flavor-mass uncertainty product and we establish that it is an upper bound to the violation of the inequalities. This finding relates temporal…

Quantum Physics · Physics 2021-12-10 Massimo Blasone , Fabrizio Illuminati , Luciano Petruzziello , Luca Smaldone

We formulate a spatial extension of the Leggett-Garg inequality by considering three distant observers locally measuring a many-body system at three subsequent times. The spatial form, in particular, is specially suited to analyze…

Quantum Physics · Physics 2025-07-08 Guillem Müller-Rigat , Donato Farina , Maciej Lewenstein , Andrea Tononi

Recently, the notion of a quantum acceleration limit has been proposed for any unitary time evolution of quantum systems governed by arbitrary nonstationary Hamiltonians. This limit articulates that the rate of change over time of the…

Quantum Physics · Physics 2026-05-29 Carlo Cafaro , Walid Redjem , Paul M. Alsing , Newshaw Bahreyni , Christian Corda

We assess non-Markovianity of a quantum open-system dynamics through the violation of temporal bell-like inequalities in a controllable Nuclear Magnetic Resonance system. We investigate experimentally the connections between the violation…

We consider two protocols for the measurement of the temporal correlation functions of a dichotomic variable Q appearing in Leggett-Garg type inequalities. The protocols measure solely whether Q has the same or different sign at the ends of…

Quantum Physics · Physics 2016-12-07 J. J. Halliwell

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

Temporal steering and violation of the Leggett-Garg inequality are two different ways of probing the violation of macro-realistic assumptions in quantum mechanics. It is shown here that under unitary evolution and projective measurements…

Quantum Physics · Physics 2016-11-18 Shiladitya Mal , Archan S. Majumdar , Dipankar Home

We investigate how discrete internal degrees of freedom in a quasi-macroscopic system affect the violation of the Leggett--Garg inequality, a test of macroscopic-realism based on temporal correlation functions. As a specific example, we…

Recent advances in non-Hermitian physical systems have led to numerous novel optical phenomena and applications. However, most realizations are limited to classical systems and quantum fluctuations of light is unexplored. For the first…

Quantum Physics · Physics 2020-01-24 Wanxia Cao , Xingda Lu , Xin Meng , Jian Sun , Heng Shen , Yanhong Xiao

The Bell-type (spatial), Kochen-Specker (contextuality) or Leggett-Garg (temporal) inequalities are based on classically plausible but otherwise quite distinct assumptions. For any of these inequalities, satisfaction is equivalent to a…

Quantum Physics · Physics 2014-02-20 Siddhartha Das , S. Aravinda , R. Srikanth , Dipankar Home

The intriguing physical phenomena associated with exceptional points have established non-Hermitian physics as a frontier of modern research. Recent investigations have extended non-Hermitian physics into the fully quantum domain. However,…

Quantum Physics · Physics 2025-11-25 Pei-Rong Han , Huiye Qiu , Hao-Long Zhang , Wen Ning , Zhen-Biao Yang , Shi-Biao Zheng

We study Leggett-Garg inequalities (LGIs) for a two level system (TLS) undergoing Markovian dynamics described by unital maps. We find analytic expression of LG parameter $K_{3}$ (simplest variant of LGIs) in terms of the parameters of two…

Quantum Physics · Physics 2023-04-25 Sayan Ghosh , Anant V. Varma , Sourin Das

Quantum mechanics presents peculiar properties that, on the one hand, have been the subject of several theoretical and experimental studies about its very foundations and, on the other hand, provide tools for developing new technologies,…