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An issue which has attracted increasing attention in contemporary researches are Kirkwood--Dirac quasiprobabilities. List of their use includes many questions of quantum physics. Applications of complex tight frames in quantum information…

Quantum Physics · Physics 2024-07-12 Alexey E. Rastegin

Mixtures of coherent states are commonly regarded as classical. Here we show that there is a quantum advantage in discriminating between coherent states in a mixture, implying the presence of quantum properties in the mixture, which are…

Quantum Physics · Physics 2018-02-26 I. Starshynov , J. Bertolotti , J. Anders

Quantum Darwinism (QD) proposes that classical objectivity emerges from the broadcast of information about a microscopic degree of freedom into multiple fractions of a many-body environment. Such a broadcast of information is in sharp…

Quantum Physics · Physics 2024-04-01 Benoît Ferté , Xiangyu Cao

As a phenomenon encompassing measurement incompatibility and Bell nonlocality, quantum contextuality is not only central to our understanding of quantum mechanics, but also an essential resource in many quantum information processing tasks.…

Quantum Physics · Physics 2024-03-19 Xiao-Dong Yu , Isadora Veeren , Otfried Gühne

The Kolmogorov consistency condition (KCC) defines the statistical boundary between classical and quantum dynamics. Its violation signifies the breakdown of a classical Markov description of temporal correlations. In this work, we establish…

Quantum Physics · Physics 2026-01-06 Arghya Maity , Ahana Ghoshal , Kelvin Onggadinata , Teck Seng Koh

The Kirkwood-Dirac quasiprobability distribution, intimately connected with the quantum correlation function of two observables measured at distinct times, is becoming increasingly relevant for fundamental physics and quantum technologies.…

We show that a quantum state may be represented as the sum of a joint probability and a complex quantum modification term. The joint probability and the modification term can both be observed in successive projective measurements. The…

Quantum Physics · Physics 2007-11-21 Lars M. Johansen

Quantum non-demolition measurements facilitate various quantum technologies, including quantum communication. Notably, their operational structure can be replicated by a classical model--referred to as a noncontextual model--making it…

Quantum Physics · Physics 2026-03-31 Min Namkung , Ilhwan Kim , Hyang-Tag Lim

We develop a comprehensive analysis of the Kirkwood-Dirac distributions in classical optics, revealing their deep connection with optical coherence as fundamental concept in optics. From their very definition, the Kirkwood-Dirac…

Quantum Physics · Physics 2026-04-10 Alfredo Luis , Lorena Ballesteros Ferraz

We establish the nonclassicality of continuous-variable states as a resource for quantum metrology. Based on the quantum Fisher information of multimode quadratures, we introduce the metrological power as a measure of nonclassicality with a…

Quantum Physics · Physics 2019-02-06 Hyukjoon Kwon , Kok Chuan Tan , Tyler Volkoff , Hyunseok Jeong

We derive and implement a general method to characterize the nonclassicality in compound discrete- and continuous-variable systems. For this purpose, we introduce the operational notion of conditional hybrid nonclassicality which relates to…

Quantum Physics · Physics 2017-09-29 E. Agudelo , J. Sperling , L. S. Costanzo , M. Bellini , A. Zavatta , W. Vogel

Identifying when observed statistics cannot be explained by any reasonable classical model is a central problem in quantum foundations. A principled and universally applicable approach to defining and identifying nonclassicality is given by…

We construct a class of systems for which quantum dynamics can be expanded around a mean field approximation with essentially classical content. The modulus of the quantum overlap of mean field states naturally introduces a classical…

The probability density distributions for the ground states of certain model systems in quantum mechanics and for their classical counterparts are considered. It is shown, that classical distributions are remarkably improved by…

Quantum Physics · Physics 2025-01-23 Tomasz Radozycki

In this paper, we investigate the Kirkwood-Dirac nonclassicality and uncertainty diagram based on discrete Fourier transform (DFT) in a $d$ dimensional system. The uncertainty diagram of complete incompatibility bases $\mathcal {A},\mathcal…

Quantum Physics · Physics 2023-08-03 Ying-Hui Yang , Bing-Bing Zhang , Xiao-Li Wang , Shi-Jiao Geng , Pei-Ying Chen

Quantum key distribution (QKD) is the most widely studied quantum cryptographic model that exploits quantum effects to achieve information-theoretically secure key establishment. Conventional QKD contains public classical post-processing…

Quantum Physics · Physics 2026-01-07 Zixuan Hu , Zhenyu Li

We define the Kirkwood-Dirac quasiprobability representation of quantum mechanics associated with the Fourier transform over second countable locally compact abelian groups. We discuss its link with the Kohn-Nirenberg quantization of the…

Quantum Physics · Physics 2026-02-23 Matéo Spriet

Two topics, evolving rapidly in separate fields, were combined recently: The out-of-time-ordered correlator (OTOC) signals quantum-information scrambling in many-body systems. The Kirkwood-Dirac (KD) quasiprobability represents operators in…

Quantum Physics · Physics 2018-04-12 Nicole Yunger Halpern , Brian Swingle , Justin Dressel

Quantum Key Distribution (QKD) is a technology that ensures secure communication by leveraging the principles of quantum mechanics, such as the no-cloning theorem and quantum uncertainty. This chapter provides an overview of this quantum…

Quantum Physics · Physics 2026-02-27 Sebastian Kish , Josef Pieprzyk , Seyit Camtepe

Nonclassical states of light are necessary resources for quantum technologies such as cryptography, computation and the definition of metrological standards. Observing signatures of nonclassicality generally requires inferring either the…

Quantum Physics · Physics 2013-05-23 Tim J. Bartley , Gaia Donati , Xian-Min Jin , Animesh Datta , Marco Barbieri , Ian A. Walmsley