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Temporal quantum states generalize the multipartite density operator formalism to the time domain, enabling a unified treatment of quantum systems with both timelike and spacelike correlations. Despite a growing body of temporal state…

Quantum Physics · Physics 2026-01-12 Zhian Jia , Kavan Modi , Dagomir Kaszlikowski

The study of measurements in quantum mechanics exposes many of the ways in which the quantum world is different. For example, one of the hallmarks of quantum mechanics is that observables may be incompatible, implying among other things…

Quantum Physics · Physics 2025-10-15 Emery Doucet , Sebastian Deffner

We discuss the (re-)construction of quasiprobability representations from generic measurements, including noisy ones. Based on the measurement under study, quasiprobabilities and the associated concept of nonclassicality are introduced. A…

Quantum Physics · Physics 2025-11-07 Jan Sperling , Laura Ares , Elizabeth Agudelo

Among the many quasiprobability representations of quantum mechanics, the family of Kirkwood-Dirac (KD) representations has come to the foreground in recent years. Each such KD representation is determined by the choice of two complementary…

Quantum Physics · Physics 2026-05-29 Matéo Spriet , Christopher Langrenez , Raymond Brummelhuis , Stephan De Bièvre

The Kirkwood-Dirac (KD) quasiprobability distribution is a fundamental representation for quantum states and has been widely applied in quantum metrology, quantum chaos, weak values in recent years. A quantum state is KD-classical if its…

Quantum Physics · Physics 2026-03-17 Lin-Yan Cai , Ying-Hui Yang , Zhu-Jun Zheng

We determine the Kirkwood-Dirac quasiprobability (KDQ) distribution associated to the stochastic instances of internal energy variations for the quantum system and environment particles in coherent Markovian collision models. In the case…

Quantum Physics · Physics 2025-07-23 Marco Pezzutto , Gabriele De Chiara , Stefano Gherardini

We provide an in-depth study of the recently introduced notion of completely incompatible observables and its links to the support uncertainty and to the Kirkwood-Dirac nonclassicality of pure quantum states. The latter notion has recently…

Quantum Physics · Physics 2023-04-04 Stephan De Bievre

Weak values and Kirkwood--Dirac (KD) quasiprobability distributions have been independently associated with both foundational issues in quantum theory and advantages in quantum metrology. We propose simple quantum circuits to measure weak…

The Kirkwood-Dirac distribution, serving as an informationally complete representation of a quantum state, has recently garnered increasing attention. We investigate the Kirkwood-Dirac classicality with respect to mutually unbiased bases.…

Quantum Physics · Physics 2025-06-11 Yan Liu , Zhihua Guo , Zhihao Ma , Shao-Ming Fei

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

Measurement in quantum mechanics is notoriously unpredictable. The uncertainty in quantum measurement can arise from the noncommutativity between the state and the measurement basis which is intrinsically quantum, but it may also be of…

Quantum Physics · Physics 2024-12-17 Agung Budiyono

What is the minimal time until a quantum system can exhibit genuine quantum features? To answer this question we derive quantum speed limits for two-time correlation functions arising from statistics of measurements. Generally, these…

Quantum Physics · Physics 2025-05-27 Sagar Silva Pratapsi , Sebastian Deffner , Stefano Gherardini

What does it take for real-deterministic c-valued (i.e., classical, commuting) variables to comply with the Heisenberg uncertainty principle? Here, we construct a class of real-deterministic c-valued variables out of the weak values…

Quantum Physics · Physics 2021-06-23 Agung Budiyono , Hermawan K. Dipojono

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.…

In this tutorial, we present the definition, interpretation and properties of some of the main quasiprobabilities that can describe the statistics of measurement outcomes evaluated at two or more times. Such statistics incorporate the…

Quantum Physics · Physics 2024-09-23 Stefano Gherardini , Gabriele De Chiara

We introduce an experimental test for ruling out classical explanations for the statistics obtained when measuring arbitrary observables at arbitrary times using individual detectors. This test requires some trust in the measurements,…

Quantum Physics · Physics 2019-03-27 Patrick P. Potts

The problem of how to obtain quasi-classical states for quantum groups is examined. A measure of quantum indeterminacy is proposed, which involves expectation values of some natural quantum group operators. It is shown that within any…

q-alg · Mathematics 2008-02-03 R. Delbourgo , R. B. Zhang

We investigate features of the quasi-joint-probability distribution for finite-state quantum systems, especially the two-state and three-state quantum systems, comparing different types of quasi-joint-probability distributions based on the…

Quantum Physics · Physics 2024-04-01 Shun Umekawa , Jaeha Lee , Naomichi Hatano

Quantum Darwinism explains how tenets of classical reality, such as objectivity and repeatability, emerge within a quantum universe. As a mathematical framework, Quantum Darwinism also provides guiding principles that determine what…

Quantum Physics · Physics 2026-01-12 Emery Doucet , Sebastian Deffner

Quasiprobability representations are well-established tools in quantum information science, with applications ranging from the classical simulability of quantum computation to quantum process tomography, quantum error correction, and…