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Counterfactual Definiteness
In quantum mechanics, counterfactual definiteness (CFD) is the ability to speak "meaningfully" of the definiteness of the results of measurements that have not been performed (i.e., the ability to assume the existence of objects, and properties of objects, even when they have not been measured). The term "counterfactual definiteness" is used in discussions of physics calculations, especially those related to the phenomenon called quantum entanglement and those related to the Bell inequalities. In such discussions "meaningfully" means the ability to treat these unmeasured results on an equal footing with measured results in statistical calculations. It is this (sometimes assumed but unstated) aspect of counterfactual definiteness that is of direct relevance to physics and mathematical models of physical systems and not philosophical concerns regarding the meaning of unmeasured results. "Counterfactual" may appear in physics discussions as a noun. What is meant in this context is "a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Mechanics
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science. Classical physics, the collection of theories that existed before the advent of quantum mechanics, describes many aspects of nature at an ordinary (macroscopic) scale, but is not sufficient for describing them at small (atomic and subatomic) scales. Most theories in classical physics can be derived from quantum mechanics as an approximation valid at large (macroscopic) scale. Quantum mechanics differs from classical physics in that energy, momentum, angular momentum, and other quantities of a bound system are restricted to discrete values ( quantization); objects have characteristics of both particles and waves (wave–particle duality); and there are limits to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asher Peres
Asher Peres ( he, אשר פרס; January 30, 1934 – January 1, 2005) was an Israeli physicist. He is well known for his work relating quantum mechanics and information theory. He helped to develop the Peres–Horodecki criterion for quantum entanglement, as well as the concept of quantum teleportation, and collaborated with others on quantum information and special relativity. He also introduced the Peres metric and researched the Hamilton–Jacobi–Einstein equation in general relativity. With Mario Feingold, he published work in quantum chaos that is known to mathematicians as the Feingold–Peres conjecture and to physicists as the Feingold–Peres theory. Life According to his autobiography, he was born ''Aristide Pressman'' in Beaulieu-sur-Dordogne in France, where his father, a Polish electrical engineer, had found work laying down power lines. He was given the name ''Aristide'' at birth, because the name his parents wanted, ''Asher'', the name of his maternal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wheeler's Delayed Choice Experiment
Wheeler's delayed-choice experiment describes a family of thought experiments in quantum physics proposed by John Archibald Wheeler, with the most prominent among them appearing in 1978 and 1984. These experiments are attempts to decide whether light somehow "senses" the experimental apparatus in the double-slit experiment it travels through, adjusting its behavior to fit by assuming the appropriate determinate state for it, or whether light remains in an indeterminate state, exhibiting both wave-like and particle-like behavior until measured. The common intention of these several types of experiments is to first do something that, according to some hidden-variable models, would make each photon "decide" whether it was going to behave as a particle or behave as a wave, and then, before the photon had time to reach the detection device, create another change in the system that would make it seem that the photon had "chosen" to behave in the opposite way. Some interpreters of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superdeterminism
In quantum mechanics, superdeterminism is a loophole in Bell's theorem. By postulating that all systems being measured are correlated with the choices of which measurements to make on them, the assumptions of the theorem are no longer fulfilled. A hidden variables theory which is superdeterministic can thus fulfill Bell's notion of local causality and still violate the inequalities derived from Bell's theorem. This makes it possible to construct a local hidden-variable theory that reproduces the predictions of quantum mechanics, for which a few toy models have been proposed. In addition to being deterministic, superdeterministic models also postulate correlations between the state that is measured and the measurement setting. Overview Bell's theorem assumes that the measurements performed at each detector can be chosen independently of each other and of the hidden variables that determine the measurement outcome. This relation is often referred to as measurement independence or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scientific Realism
Scientific realism is the view that the universe described by science is real regardless of how it may be interpreted. Within philosophy of science, this view is often an answer to the question "how is the success of science to be explained?" The discussion on the success of science in this context centers primarily on the status of unobservable entities apparently talked about by scientific theories. Generally, those who are scientific realists assert that one can make valid claims about unobservables (viz., that they have the same ontological status) as observables, as opposed to instrumentalism. Main features Scientific realism involves two basic positions. First, it is a set of claims about the features of an ideal scientific theory; an ideal theory is the sort of theory science aims to produce. Second, it is the commitment that science will eventually produce theories very much like an ideal theory and that science has done pretty well thus far in some domains. It is imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Renninger Negative-result Experiment
In quantum mechanics, the Renninger negative-result experiment is a thought experiment that illustrates some of the difficulties of understanding the nature of wave function collapse and measurement in quantum mechanics. The statement is that a particle need not be detected in order for a quantum measurement to occur, and that the lack of a particle detection can also constitute a measurement. The thought experiment was first posed in 1953 by Mauritius Renninger. It can be understood to be a refinement of the paradox presented in the Mott problem. The Mott problem The Mott problem concerns the paradox of reconciling the spherical wave function describing the emission of an alpha ray by a radioactive nucleus, with the linear tracks seen in a cloud chamber. Formulated in 1929 by Sir Nevill Francis Mott and Werner Heisenberg, it was resolved by a calculation done by Mott that showed that the correct quantum mechanical system must include the wave functions for the atoms in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Indeterminacy
Quantum indeterminacy is the apparent ''necessary'' incompleteness in the description of a physical system, that has become one of the characteristics of the standard description of quantum physics. Prior to quantum physics, it was thought that :(a) a physical system had a determinate state which uniquely determined all the values of its measurable properties, and :(b) conversely, the values of its measurable properties uniquely determined the state. Quantum indeterminacy can be quantitatively characterized by a probability distribution on the set of outcomes of measurements of an observable. The distribution is uniquely determined by the system state, and moreover quantum mechanics provides a recipe for calculating this probability distribution. Indeterminacy in measurement was not an innovation of quantum mechanics, since it had been established early on by experimentalists that errors in measurement may lead to indeterminate outcomes. By the later half of the 18th century, m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naive Realism
Naivety (also spelled naïvety), naiveness, or naïveté is the state of being naive. It refers to an apparent or actual lack of experience and sophistication, often describing a neglect of pragmatism in favor of moral idealism. A ''naïve'' may be called a ''naïf''. Etymology In its early use, the word ''naïve'' meant "natural or innocent", and did not connote ineptitude. As a French adjective, it is spelled ''naïve'', for feminine nouns, and ''naïf'', for masculine nouns. As a French noun, it is spelled ''naïveté''. It is sometimes spelled "naïve" with a diaeresis, but as an unitalicized English word, "naive" is now the more usual spelling. "naïf" often represents the French masculine, but has a secondary meaning as an artistic style. “Naïve” is pronounced as two syllables, in the French manner, and with the stress on the second one. Culture The naïf appears as a cultural type in two main forms. On the one hand, there is 'the satirical naïf, such as Candide'. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interaction-free Measurement
In physics, interaction-free measurement is a type of measurement in quantum mechanics that detects the position, presence, or state of an object without an interaction occurring between it and the measuring device. Examples include the Renninger negative-result experiment In quantum mechanics, the Renninger negative-result experiment is a thought experiment that illustrates some of the difficulties of understanding the nature of wave function collapse and measurement in quantum mechanics. The statement is that a pa ..., the Elitzur–Vaidman bomb-testing problem, and certain double-cavity optical systems, such as Hardy's paradox. In Quantum Computation such measurements are referred to as Counterfactual Quantum Computation, an idea introduced by physicists Graeme Mitchinson and Richard Jozsa. Examples include Keith Bowden's Counterfactual Mirror ArrayBowden, Keith G, "Classical Computation can be Counterfactual", in Aspects I, Proc ANPA19, Cambridge 1997 (published May 1999), des ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Determinism
Determinism is a philosophical view, where all events are determined completely by previously existing causes. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes overlapping motives and considerations. The opposite of determinism is some kind of indeterminism (otherwise called nondeterminism) or randomness. Determinism is often contrasted with free will, although some philosophers claim that the two are compatible.For example, see Determinism is often used to mean ''causal determinism'', which in physics is known as cause-and-effect. This is the concept that events within a given paradigm are bound by causality in such a way that any state of an object or event is completely determined by its prior states. This meaning can be distinguished from other varieties of determinism mentioned below. Debates about determinism often concern the scope of determined systems; some maintain that the entire universe is a single determina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Griffiths (physicist)
Robert B. Griffiths (February 25, 1937) is an American physicist at Carnegie Mellon University. He is the originator of the consistent histories approach to quantum mechanics, which has since been developed by himself, Roland Omnès, Murray Gell-Mann, and James Hartle. Early life and education Robert B. Griffiths was born in Etah, Uttar Pradesh in 1937 to Presbyterian missionaries. Griffiths attended Woodstock School, India from fourth standard to tenth, along with his brothers and sisters. Even during his Woodstock days, Griffiths' mathematical and scientific aptitude was apparent. The 1952 year book remarks that ''"Robert is famous for his long arguments (and unsurpassed knowledge) in chemistry class, his ability to 'recite' the log tables indelibly written in his brain, and his skill when it comes to fixing anything electrical."'' This knack for electrical systems kept Griffiths at Woodstock through part of 1953, working with the school's various wiring systems. Academic career ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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