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Classical and quantum measurement theories are usually held to be different because the algebra of classical measurements is commutative, however the Poisson bracket allows noncommutativity to be added naturally. After we introduce…

Quantum Physics · Physics 2022-01-19 Peter Morgan

One of the most difficult problems in quantum mechanics is the analysis of the measurement processes. In this paper, we point out that many of these difficulties originate from the different roles of measurement outcomes and observable…

Quantum Physics · Physics 2017-06-08 Taiki Nii , Masataka Iinuma , Holger F. Hofmann

Measurement is an important scientific activity. In most of science, including classical physics, is may be understood as a way of finding out about the physical world and representing the results numerically. No-go theorems show that…

Quantum Physics · Physics 2026-05-18 Richard Healey

Classical learning of the expectation values of observables for quantum states is a natural variant of learning quantum states or channels. While learning-theoretic frameworks establish the sample complexity and the number of measurement…

Quantum Physics · Physics 2024-08-12 Beng Yee Gan , Po-Wei Huang , Elies Gil-Fuster , Patrick Rebentrost

In the classical world one can construct two identical systems which have identical behavior and give identical measurement results. We show this to be impossible in the quantum domain. We prove that after the same quantum measurement two…

Quantum Physics · Physics 2017-01-10 Denis Sych , Gerd Leuchs

A small quantum scattering system (the microsystem) is studied in interaction with a large system (the macrosystem) described by unknown stochastic variables. The interaction between the two systems is diagonal for the microsystem in a…

Quantum Physics · Physics 2007-05-23 K. -E. Eriksson

We consider highly inaccurate measurements made on classical stochastic and quantum systems. In the quantum case such a \e{weak} measurement preserves coherence between the system's alternatives. We demonstrate that in both cases the…

Quantum Physics · Physics 2026-03-16 D. Sokolovski , D. Alonso , S. Brouard

Superposition is the core feature that sets quantum theory apart from classical physics. Here, we investigate whether sets of quantum measurements can be modelled by using only devices that are operationally classical, in the sense that…

Quantum Physics · Physics 2026-03-30 Gabriele Cobucci , Alexander Bernal , Roope Uola , Armin Tavakoli

We show that the so-called quantum probabilistic rule, usually presented in the physical literature as an argument of the essential distinction between the probability relations under quantum and classical measurements, is not, as it is…

Quantum Physics · Physics 2019-11-19 Andrei Khrennikov , Elena Loubenets

Measurements serve as the intermediate communication layer between the quantum world and our classical perception. So, the question which measurements efficiently extract information from quantum systems is of central interest. Using…

Quantum Physics · Physics 2020-12-14 H. Chau Nguyen , Otfried Gühne

The claim that there is an inconsistency of quantum-classical dynamics [1] is investigated. We point out that a consistent formulation of quantum and classical dynamics which can be used to describe quantum measurement processes is already…

Quantum Physics · Physics 2007-05-23 E. C. G. Sudarshan

Classical Bayes' rule lays the foundation for the classical causal relation between cause (input) and effect (output). This causal relation is believed to be universally true for all physical processes. Here we show, on the contrary, that…

Quantum Physics · Physics 2022-07-19 Mohit Lal Bera , Manabendra Nath Bera

Measurement uncertainty and experimental error are important concepts taught in undergraduate physics laboratories. Although student ideas about error and uncertainty in introductory classical mechanics lab experiments have been studied…

Physics Education · Physics 2021-09-20 Emily M. Stump , Courtney L. White , Gina Passante , N. G. Holmes

The ability to perform a universal set of quantum operations based solely on static resources and measurements presents us with a strikingly novel viewpoint for thinking about quantum computation and its powers. We consider the two major…

Quantum Physics · Physics 2007-05-23 Panos Aliferis , Debbie W. Leung

Many of the conceptual problems students have in understanding quantum mechanics arise from the way probabilities are introduced in standard (textbook) quantum theory through the use of measurements. Introducing consistent microscopic…

Quantum Physics · Physics 2007-05-23 Robert B. Griffiths

In this paper, we present a thought experiment that demonstrates that the equivalence of quantum reduced states and statistical mixed states of ensembles is not merely a simple mathematical formulation in quantum mechanics, but rather…

Quantum Physics · Physics 2025-04-18 Zhihong Zuo

Quantum dynamics of the collective mode and individual particles on a ring is studied as the simplest model of projective quantum measurement. In this model, the collective mode measures an individual single quantum system. The heart of the…

Quantum Physics · Physics 2015-06-19 Masahiro Morikawa , Akika Nakamichi

Quantum theory in its conventional formulation is notoriously subject to various measurement-related paradoxes, as exemplified by the "Schrodinger's Cat" and "Wigner's Friend" thought experiments. It has been shown, for example by…

Quantum Physics · Physics 2024-10-04 R. E. Kastner

The quantum theory of measurement has been a matter of debate for over eighty years. Most of the discussion has focused on theoretical issues with the consequence that operational prescriptions, which are integral to experimental physics,…

History and Philosophy of Physics · Physics 2013-09-04 Stephen Boughn , Marcel Reginatto

Quantum mechanics is derived from the principle that the universe contain as much variety as possible, in the sense of maximizing the distinctiveness of each subsystem. The quantum state of a microscopic system is defined to correspond to…

Quantum Physics · Physics 2016-03-23 Lee Smolin