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The notion of trajectory of an individual particle is strictly inhibited in quantum mechanics because of the uncertainty principle. Nonetheless, the weak value, which has been proposed as a novel and measurable quantity definable to any…

Quantum Physics · Physics 2015-04-01 Takuya Mori , Izumi Tsutsui

The transition from classical to quantum mechanics rests on the recognition that the structure of information is not what we thought it was: there are operational, i.e., phenomenal, probabilistic correlations that lie outside the polytope…

Quantum Physics · Physics 2015-06-11 Jeffrey Bub

Traditionally causes come before effects, but according to modern physics things aren't that simple. Special relativity shows that `before' and `after' are relative, and quantum measurement is even more subtle. Since the nonlocality of…

Quantum Physics · Physics 2009-09-25 Ian C. Percival

Negative and complex numbers are so familiar in modern mathematics, physics, and engineering that it is easy to forget how uncertain their status once was. They did not become established through a single route. This article follows four…

Optics · Physics 2026-03-24 Alex Krasnok

The fact that the probability density expression provided by the Klein-Gordon equation can take on negative values is usually seen as an obstacle to formulating a particle interpretation of quantum mechanics. Nevertheless, reconciling this…

Quantum Physics · Physics 2025-02-24 Roderick Sutherland

We consider a thought experiment where the preparation of a macroscopically massive or charged particle in a quantum superposition and the associated dynamics of a distant test particle apparently allow for superluminal communication. We…

Quantum Physics · Physics 2016-03-10 Andrea Mari , Giacomo De Palma , Vittorio Giovannetti

Following J.-Y.B\'eziau in his pioneer work on non-standard interpretations of the traditional square of opposition, we have applied the abstract structure of the square to study the relation of opposition between states in superposition in…

Quantum Physics · Physics 2014-06-10 Jonas R. B. Arenhart , Décio Krause

The purpose of this article is to show that the introduction of hidden variables to describe individual events is fully consistent with the statistical predictions of quantum theory. We illustrate the validity of this assertion by…

General Physics · Physics 2007-08-07 L. Fritsche , M. Haugk

As it is well-known one of the most fascinating examples in remarkable discussion between Einstein and Bohr on the conceptual foundation of the quantum mechanics (Heisenberg energy-time uncertainty relation especially) was an experimental…

Quantum Physics · Physics 2009-12-22 Vladan Pankovic , Darko V. Kapor

A simple minimalist argument is given for why some correlations between quantum systems boggle our classical intuition. The argument relies on two elementary physical assumptions, and recovers the standard experimentally-testable Bell…

Quantum Physics · Physics 2024-08-29 Michael J. W. Hall

A precise definition of "weak [quantum] measurements" and "weak value" (of a quantum observable) is offered, and simple finite dimensional examples are given showing that weak values are not unique and therefore probably do not correspond…

Quantum Physics · Physics 2009-10-01 Stephen Parrott

Unlike regular time evolution governed by the Schr\"odinger equation, standard quantum measurement appears to violate time-reversal symmetry. Measurement creates random disturbances (e.g., collapse) that prevents back-tracing the quantum…

Research on strongly correlated electron systems faces a fundamental challenge due to the complex nature of intrinsic many-body correlations. A key strategy to address this challenge lies in advancing experimental methods that can directly…

Strongly Correlated Electrons · Physics 2026-03-31 Yuehua Su , Guoya Zhang , Chao Zhang , Dezhong Cao

The projective measurement usually destroys the quantum correlation between two subsystems of a composite system, thereby making the measured state useless for any efficient quantum information processing and quantum computation task. The…

Quantum Physics · Physics 2014-05-02 Uttam Singh , Arun Kumar Pati

The black hole information paradox tells us something important about the way quantum mechanics and gravity fit together. In these lectures I try to give a pedagogical review of the essential physics leading to the paradox, using mostly…

High Energy Physics - Theory · Physics 2009-01-28 Samir D. Mathur

Entanglement of light and matter is an essential resource for effective quantum engineering. In particular, collective states of atomic ensembles are robust against decoherence while preserving the possibility of strong interaction with…

Quantum Physics · Physics 2017-02-20 Michał Dąbrowski , Michał Parniak , Wojciech Wasilewski

The so-called Simpson's "paradox", or Yule-Simpson (YS) effect, occurs in classical statistics when the correlations that are present among different sets of samples are reversed if the sets are combined together, thus ignoring one or more…

Quantum Physics · Physics 2015-06-04 Matteo G. A. Paris

Contextuality and nonlocality are two fundamental properties of nature. Hardy's proof is considered the simplest proof of nonlocality and can also be seen as a particular violation of the simplest Bell inequality. A fundamental question is:…

Quantum Physics · Physics 2013-11-01 Adan Cabello , Piotr Badziag , Marcelo Terra Cunha , Mohamed Bourennane

It is shown that Quantum Mechanics is ambiguous when predicting relative frequencies for an entangled system if the measurements of both subsystems are performed in spatially separated events. This ambiguity gives way to unphysical…

Quantum Physics · Physics 2016-01-27 Carlos Lopez

Physical superpositions exist both in classical and in quantum physics. However, what is exactly meant by 'superposition' in each case is extremely different. In this paper we discuss some of the multiple interpretations which exist in the…

Quantum Physics · Physics 2015-06-16 Newton da Costa , Christian de Ronde