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In general, a quantum measurement yields an undetermined answer and alters the system to be consistent with the measurement result. This process maps multiple initial states into a single state and thus cannot be reversed. This has…

Quantum mechanics and the theory of gravity are presently not compatible. A particular question is whether gravity causes decoherence - an unavoidable source of noise. Several models for gravitational decoherence have been proposed, not all…

Quantum Physics · Physics 2018-05-16 C. Pfister , J. Kaniewski , M. Tomamichel , A. Mantri , R. Schmucker , N. McMahon , G. Milburn , S. Wehner

The challenge of understanding quantum measurement persists as a fundamental issue in modern physics. Particularly, the abrupt and energy-non-conserving collapse of the wave function appears to contradict classical thermodynamic laws. The…

Quantum Physics · Physics 2026-03-10 Sophie Engineer , Tom Rivlin , Sabine Wollmann , Mehul Malik , Maximilian P. E. Lock

In this work we investigate the relation between quantum measurements and decoherence, in order to formally express the necessity of the latter for obtaining an informative output from the former. To this aim, referring to the Von Neumann…

Quantum Physics · Physics 2015-06-23 Pietro Liuzzo-Scorpo , Alessandro Cuccoli , Paola Verrucchi

Symmetry, irreversibility, and quantum coherence are foundational concepts in physics. Here, we present a universal tradeoff relation between these three concepts. This particularly reveals that (1) under a global symmetry, any attempt to…

Quantum Physics · Physics 2025-01-29 Hiroyasu Tajima , Ryuji Takagi , Yui Kuramochi

The quantum measurement problem, the unresolved conflict between the unitary evolution of the wave function and the postulate of wave function collapse, remains the most profound conceptual challenge in quantum foundations. While…

Quantum Physics · Physics 2025-09-17 Eyad I. B Hamid

The existence of incompatible measurements, i.e. measurements which cannot be performed simultaneously on a single copy of a quantum state, constitutes an important distinction between quantum mechanics and classical theories. While…

Quantum Physics · Physics 2022-06-22 Krzysztof Mordasewicz , Jędrzej Kaniewski

It is widely known that `collapse of the wave function' on a quantum system A may be brought about by an interaction with another quantum system B. We will prove that this is not just a possible, but a necessary consequence of information…

Quantum Physics · Physics 2007-05-23 Bas Janssens

Coherence and entanglement are fundamental properties of quantum systems, promising to power the near future quantum computers, sensors and simulators. Yet, their experimental detection is challenging, usually requiring full reconstruction…

Quantum Physics · Physics 2017-08-01 Graeme Smith , John A. Smolin , Xiao Yuan , Qi Zhao , Davide Girolami , Xiongfeng Ma

I discuss some of the main interpretations given to explain the indeterministic nature of quantum measurements and show that all has some loopholes in one corner or another. I propose an alternative interpretation based on the notion of…

Quantum Physics · Physics 2009-09-30 M. B. Altaie

The speculation that gravity is the key to solving the quantum measurement problem has been alive for decades, without any convincing demonstration of a solution. One necessary factor in the relevant proposals is that the gravitational…

Quantum Physics · Physics 2021-06-01 C. S. Unnikrishnan , George T. Gillies

The measurement process of observables in a quantum system comes out to be an unsovable problem which started in the early times of the development of the theory. In the present note we consider the measured system part of an open system…

Quantum Physics · Physics 2023-12-21 Jean Richert , Tarek Khalil

Quantum coherence is an essential ingredient in quantum information processing and plays a central role in emergent fields such as nanoscale thermodynamics and quantum biology. However, our understanding and quantitative characterization of…

Preserving the precision of the parameter of interest in the presence of environmental decoherence is an important yet challenging task in dissipative quantum sensing. In this work, we study quantum metrology when the decoherence effect is…

Quantum Physics · Physics 2024-11-05 Jing Yang

Quantum coherence is the most fundamental feature of quantum mechanics. The usual understanding of it depends on the choice of the basis, that is, the coherence of the same quantum state is different within different reference framework. To…

Quantum Physics · Physics 2017-04-17 Chang-shui Yu , Yi-ren Yang , Bao-qing Guo

In this essay, we argue that certain aspects of the measurement require revision in Quantum Gravity. Using entropic arguments, we propose that the number of measurement outcomes and the accuracy (or the range) of the measurement are limited…

High Energy Physics - Theory · Physics 2024-08-28 Juanca Carrasco-Martinez

The uncertainty principle sets limit on our ability to predict the values of two incompatible observables measured on a quantum particle simultaneously. This principle can be stated in various forms. In quantum information theory, it is…

Quantum Physics · Physics 2018-09-27 H. Dolatkhah , S. Haseli , S. Salimi , S. A. Khorashad

Two thought experiments are analyzed, revealing that the quantum state of the universe does not contain definitive evidence of the wavefunction collapse. The first thought experiment shows that unitary quantum evolution alone can account…

Quantum Physics · Physics 2017-09-08 Ovidiu Cristinel Stoica

Quantum measurement finds the observed system in a collapsed state, rather than in the state predicted by the Schr\"odinger equation. Yet there is a relatively spread opinion that the wavefunction collapse can be explained by unitary…

Quantum Physics · Physics 2016-02-08 Ovidiu Cristinel Stoica

The fact that there are quantum observables without a simultaneous measurement is one of the fundamental characteristics of quantum mechanics. In this work we expand the concept of joint measurability to all kinds of possible measurement…

Quantum Physics · Physics 2014-02-19 Teiko Heinosaari , Takayuki Miyadera , Daniel Reitzner