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We consider the problem of determining the state of a quantum system given one or more readings of the expectation value of an observable. The system is assumed to be a finite dimensional quantum control system for which we can influence…

Quantum Physics · Physics 2009-11-10 Domenico D'Alessandro

The quantum mechanical measurement problem is the difficulty of dealing with the indefiniteness of the pointer observable at the conclusion of a measurement process governed by unitary quantum dynamics. There has been hope to solve this…

Quantum Physics · Physics 2007-05-23 P. Busch , A. Shimony

Since the advent of quantum mechanics we have mainly been concerned with its predictions from the perspective of an external observer. This is in strong contrast to the theory of general relativity, where the physics is governed by the…

Quantum Physics · Physics 2014-11-17 Dries Sels , Michiel Wouters

Quantum matter in quantum space-time is discussed using general properties of energy-conservation laws. As a rather radical conclusion, it is found that standard methods of differential geometry and quantum field theory on curved space-time…

General Relativity and Quantum Cosmology · Physics 2013-11-13 Martin Bojowald , Golam Mortuza Hossain , Mikhail Kagan , Casey Tomlin

Making measurements on single quantum systems is considered difficult, almost impossible if the state is a-priori unknown. Protective measurements suggest a possibility to measure single quantum systems and gain some new information in the…

Quantum Physics · Physics 2015-12-10 Tabish Qureshi , N. D. Hari Dass

Coherence of a quantum state intrinsically depends on the choice of the reference basis. A natural question to ask is the following: if we use two or more incompatible reference bases, can~there be some trade-off relation between the…

Quantum Physics · Physics 2016-07-20 Uttam Singh , Arun Kumar Pati , Manabendra Nath Bera

We explain the necessity of application of semi-metric in general relativity. A detailed discussion on the energy-momentum conservation in the general relativity is presented using the mathematical tool of semi-metric. By means of the…

General Relativity and Quantum Cosmology · Physics 2018-03-28 Yi-Shi Duan , Jing-Ye Zhang

Dynamics of systems of structured particles consisting of potentially interacting material points is considered in the framework of classical mechanics. Equations of interaction and motion of structured particles have been derived. The…

General Physics · Physics 2012-05-14 V. M. Somsikov

Quantum coherence, the ability to control the phases in superposition states is a resource, and it is of crucial importance, therefore, to understand how it is consumed in use. It has been suggested that catalytic coherence is possible,…

Quantum Physics · Physics 2018-09-26 Joan A. Vaccaro , Sarah Croke , Stephen M. Barnett

The physics of many closed, conservative systems can be described by both classical and quantum theories. The dynamics according to classical theory is symplectic and admits linear instabilities which would initially seem at odds with a…

Quantum Physics · Physics 2024-01-08 Michael Q. May , Hong Qin

According to Einstein's principle of general covariance, all laws of nature are to be expressed by manifestly covariant equations. In recent work, the covariant law of energy-momentum conservation has been established. Here, we show that…

General Physics · Physics 2007-05-23 Kenneth Dalton

Conditional expectation values of quantum mechanical observables reflect unique non-classical correlations, and are generally sensitive to decoherence. We consider the circumstances under which such sensitivity to decoherence is removed,…

Quantum Physics · Physics 2019-01-25 M. Hamed Mohammady , Alessandro Romito

The existence of conservation laws is one of the most important requirement of physical theories. Some of them, like energy conservation, knows no experimental exception. However, the generalization of these conservation laws to curved…

General Relativity and Quantum Cosmology · Physics 2012-08-24 J. C. Fabris

This paper gives a brief description of the derivation of a composition law for the propagator of a relativistic particle, in a sum over histories quantization. The extension of this derivation to the problem of finding a composition law…

General Relativity and Quantum Cosmology · Physics 2011-04-15 J. J. Halliwell , M. E. Ortiz

Conservation laws are time-invariant properties that constrain many physical systems. For systems of chemical reactions, the law of mass conservation constrains how atoms flow between chemical species. Chemical reaction networks can display…

Atmospheric and Oceanic Physics · Physics 2026-05-27 Beatriz Lucia G. Rodriguez , Patrick Obin Sturm , Daniel Getter , Sam J. Silva

We couple the issue of evolution in the laws of physics with that of violations of energy conservation. We define evolution in terms of time variables canonically dual to ``constants'' (such as $\Lambda$, the Planck mass or the…

High Energy Physics - Theory · Physics 2023-10-31 Joao Magueijo

This is a limited overview of quantum non-demolition (QND) measurements, with brief discussions of illustrative examples meant to clarify the essential features. In a QND measurement, the predictability of a subsequent value of a precisely…

Quantum Physics · Physics 2018-11-27 C. S. Unnikrishnan

The second law of thermodynamics states that entropy increases (or does not change) by time in an isolated system. As microscopic physical laws are reversible, the origin of irreversibility is not straightforward. Although the outcome of a…

Statistical Mechanics · Physics 2013-02-19 Balint Szabo

A covariant formula for conserved currents of energy, momentum and angular-momentum is derived from a general form of Noethers theorem applied directly to the Einstein-Hilbert action of classical general relativity. Energy conservation in a…

General Relativity and Quantum Cosmology · Physics 2008-02-03 Philip E. Gibbs

Quantum coherence quantifies the amount of superposition in a quantum system, and is the reason and resource behind several phenomena and technologies. It depends on the natural basis in which the quantum state of the system is expressed,…

Quantum Physics · Physics 2021-08-13 Ingita Banerjee , Kornikar Sen , Chirag Srivastava , Ujjwal Sen