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Leggett–Garg Inequality
The Leggett–Garg inequality, named for Anthony James Leggett and Anupam Garg, is a mathematical inequality fulfilled by all macrorealistic physical theories. Here, macrorealism (macroscopic realism) is a classical worldview defined by the conjunction of two postulates: # Macrorealism per se: "A macroscopic object, which has available to it two or more macroscopically distinct states, is at any given time in a definite one of those states." # Noninvasive measurability: "It is possible in principle to determine which of these states the system is in without any effect on the state itself, or on the subsequent system dynamics." In quantum mechanics In quantum mechanics, the Leggett–Garg inequality is violated, meaning that the time evolution of a system cannot be understood classically. The situation is similar to the violation of Bell's inequalities in Bell test experiments, which plays an important role in understanding the nature of the Einstein–Podolsky–Rosen paradox. He ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anthony James Leggett
Sir Anthony James Leggett (born 26 March 1938) is a British-American theoretical physicist and professor emeritus at the University of Illinois at Urbana-Champaign. Leggett is widely recognised as a world leader in the theory of low-temperature physics, and his pioneering work on superfluidity was recognised by the 2003 Nobel Prize in Physics. He has shaped the theoretical understanding of normal and superfluid helium liquids and strongly coupled superfluids. He set directions for research in the quantum physics of macroscopic dissipative systems and use of condensed systems to test the foundations of quantum mechanics. In a 2021 interview given to Federal University of Pará in Brazil, Leggett talks about his early life in London, his path to become a theoretical physicist and also his scientific works and collaborations. Early life and education Leggett was born in Camberwell, South London, and raised Catholic. His father's forebears were village cobblers in a small village ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MINOS
In Greek mythology, Minos (; grc-gre, Μίνως, ) was a King of Crete, son of Zeus and Europa. Every nine years, he made King Aegeus pick seven young boys and seven young girls to be sent to Daedalus's creation, the labyrinth, to be eaten by the Minotaur. After his death, Minos became a judge of the dead in the underworld. The Minoan civilization of Crete was named after him by the archaeologist Sir Arthur Evans. Etymology "Minos" is often interpreted as the Cretan word for "king", or, by a euhemerist interpretation, the name of a particular king that was subsequently used as a title. According to La Marle's reading of Linear A, which has been heavily criticised as arbitrary, we should read ''mwi-nu ro-ja'' (Minos the king) on a Linear A tablet. La Marle suggests that the name'' mwi-nu'' (Minos) is expected to mean 'ascetic' as Sanskrit ''muni'', and fits this explanation to the legend about Minos sometimes living in caves on Crete. The royal title ''ro-ja'' is read o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Measurement
In quantum physics, a measurement is the testing or manipulation of a physical system to yield a numerical result. The predictions that quantum physics makes are in general probabilistic. The mathematical tools for making predictions about what measurement outcomes may occur were developed during the 20th century and make use of linear algebra and functional analysis. Quantum physics has proven to be an empirical success and to have wide-ranging applicability. However, on a more philosophical level, debates continue about the meaning of the measurement concept. Mathematical formalism "Observables" as self-adjoint operators In quantum mechanics, each physical system is associated with a Hilbert space, each element of which represents a possible state of the physical system. The approach codified by John von Neumann represents a measurement upon a physical system by a self-adjoint operator on that Hilbert space termed an "observable". These observables play the role of measurab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inequalities
Inequality may refer to: Economics * Attention inequality, unequal distribution of attention across users, groups of people, issues in etc. in attention economy * Economic inequality, difference in economic well-being between population groups * Spatial inequality, the unequal distribution of income and resources across geographical regions * Income inequality metrics, used to measure income and economic inequality among participants in a particular economy * International inequality, economic differences between countries Healthcare * Health equity, the study of differences in the quality of health and healthcare across different populations Mathematics * Inequality (mathematics), a relation between two values when they are different Social sciences * Educational inequality, the unequal distribution of academic resources to socially excluded communities * Gender inequality, unequal treatment or perceptions of individuals due to their gender * Participation inequality, the pheno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physics Theorems
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events." Physics is one of the most fundamental scientific disciplines, with its main goal being to understand how the universe behaves. "Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. (. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interpretations Of Quantum Mechanics
An interpretation of quantum mechanics is an attempt to explain how the mathematical theory of quantum mechanics might correspond to experienced reality. Although quantum mechanics has held up to rigorous and extremely precise tests in an extraordinarily broad range of experiments, there exist a number of contending schools of thought over their interpretation. These views on interpretation differ on such fundamental questions as whether quantum mechanics is deterministic or stochastic, which elements of quantum mechanics can be considered real, and what the nature of measurement is, among other matters. Despite nearly a century of debate and experiment, no consensus has been reached among physicists and philosophers of physics concerning which interpretation best "represents" reality. History The definition of quantum theorists' terms, such as ''wave function'' and ''matrix mechanics'', progressed through many stages. For instance, Erwin Schrödinger originally viewed the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Information Science
Quantum information science is an interdisciplinary field that seeks to understand the analysis, processing, and transmission of information using quantum mechanics principles. It combines the study of Information science with quantum effects in physics. It includes theoretical issues in computational models and more experimental topics in quantum physics, including what can and cannot be done with quantum information. The term quantum information theory is also used, but it fails to encompass experimental research, and can be confused with a subfield of quantum information science that addresses the processing of quantum information. Scientific and engineering studies To understand quantum teleportation, quantum entanglement and the manufacturing of quantum computer hardware requires a thorough understanding of quantum physics and engineering. Since 2010s, there has been remarkable progress in manufacturing quantum computers, with companies like Google and IBM investing heavily ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leggett Inequality
The Leggett inequalities, named for Anthony James Leggett, who derived them, are a related pair of mathematical expressions concerning the correlations of properties of entangled particles. (As published by Leggett, the inequalities were exemplified in terms of relative angles of elliptical and linear polarizations.) They are fulfilled by a large class of physical theories based on particular non-local and realistic assumptions, that may be considered to be plausible or intuitive according to common physical reasoning. The Leggett inequalities are violated by quantum mechanical theory. The results of experimental tests in 2007 and 2010 have shown agreement with quantum mechanics rather than the Leggett inequalities. Given that experimental tests of Bell's inequalities have ruled out local realism in quantum mechanics, the violation of Leggett's inequalities is considered to have falsified realism Realism, Realistic, or Realists may refer to: In the arts *Realism (arts ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CHSH Inequality
In physics, the CHSH inequality can be used in the proof of Bell's theorem, which states that certain consequences of entanglement in quantum mechanics can not be reproduced by local hidden-variable theories. Experimental verification of the inequality being violated is seen as confirmation that nature cannot be described by such theories. CHSH stands for John Clauser, Michael Horne, Abner Shimony, and Richard Holt, who described it in a much-cited paper published in 1969. They derived the CHSH inequality, which, as with John Stewart Bell's original inequality, is a constraint on the statistical occurrence of "coincidences" in a Bell test which is necessarily true if there exist underlying local hidden variables, an assumption that is sometimes termed local realism. It is in fact the case that the inequality is routinely violated by modern experiments in quantum mechanics. Statement The usual form of the CHSH inequality is where ''a'' and ''a''′ are detector setti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Decoherence
Quantum decoherence is the loss of quantum coherence. In quantum mechanics, particles such as electrons are described by a wave function, a mathematical representation of the quantum state of a system; a probabilistic interpretation of the wave function is used to explain various quantum effects. As long as there exists a definite phase relation between different states, the system is said to be coherent. A definite phase relationship is necessary to perform quantum computing on quantum information encoded in quantum states. Coherence is preserved under the laws of quantum physics. If a quantum system were perfectly isolated, it would maintain coherence indefinitely, but it would be impossible to manipulate or investigate it. If it is not perfectly isolated, for example during a measurement, coherence is shared with the environment and appears to be lost with time; a process called quantum decoherence. As a result of this process, quantum behavior is apparently lost, just as ene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giorgio Parisi
Giorgio Parisi (born 4 August 1948) is an Italian theoretical physicist, whose research has focused on quantum field theory, statistical mechanics and complex systems. His best known contributions are the QCD evolution equations for parton densities, obtained with Guido Altarelli, known as the Altarelli–Parisi or DGLAP equations, the exact solution of the Sherrington–Kirkpatrick model of spin glasses, the Kardar–Parisi–Zhang equation describing dynamic scaling of growing interfaces, and the study of whirling flocks of birds. He was awarded the 2021 Nobel Prize in Physics jointly with Klaus Hasselmann and Syukuro Manabe for groundbreaking contributions to theory of complex systems, in particular "for the discovery of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales." Career Giorgio Parisi received his degree from the University of Rome La Sapienza in 1970 under the supervision of Nicola Cabibbo. He was a researcher at the L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anupam Garg
Anupam Garg is a professor in the department of Physics & Astronomy at Northwestern University, Illinois. He received his Ph.D. in 1983 from Cornell University. In 2012, he became a Fellow of the American Physical Society (APS) thanks to his work on molecular magnetism and macroscopic quantum phenomena. Garg is best known for formulating the Leggett–Garg inequality, named for Anthony James Leggett and himself, which is a mathematical inequality fulfilled by all macrorealistic physical theories. He is also known for the Garg-Onuchic-Ambegaokar model of charge transfer. His current research interests center around quantum and semi-classical phenomena associated with the orientation of quantum mechanical spin. Garg is the author of a graduate physics textbook, ''Classical Electromagnetism in a Nutshell''.Princeton University Press (2012). References Cornell University alumni 21st-century American physicists Northwestern University faculty Living people Year of birth miss ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
