WordNet

(physics) the smallest discrete quantity of some physical property that a system can possess (according to quantum theory)
a discrete amount of something that is analogous to the quantities in quantum theory
of or relating to a quantum or capable of existing in only one of two states (同)quantized
the branch of physics based on quantum theory

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量子
quantumの複数形

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/04/04 23:50:55」(JST)

In physics, a quantum (plural: quanta) is the minimum amount of any physical entity involved in an interaction. Behind this, one finds the fundamental notion that a physical property may be "quantized," referred to as "the hypothesis of quantization".^[1] This means that the magnitude of the physical property can take on only certain discrete values.

For example, a photon is a single quantum of (visible) light as well as a single quantum of all other forms of electromagnetic radiation, and can be referred to as a "light quantum". The energy of an electron bound to an atom is also quantized, and thus can only exist in certain discrete values. As a result, atoms are stable, and hence matter in general is stable.

As incorporated into the theory of quantum mechanics, this quantization of the energy of electrons and the resulting implications are regarded by physicists as part of the fundamental framework for understanding and describing nature.

Etymology and discovery

The word "quantum" comes from the Latin "quantus", meaning "how much". "Quanta", short for "quanta of electricity" (electrons) was used in a 1902 article on the photoelectric effect by Philipp Lenard, who credited Hermann von Helmholtz for using the word in the area of electricity. However, the word quantum in general was well known before 1900.^[2] It was often used by physicians, such as in the term quantum satis. Both Helmholtz and Julius von Mayer were physicians as well as physicists. Helmholtz used "quantum" with reference to heat in his article^[3] on Mayer's work, and indeed, the word "quantum" can be found in the formulation of the first law of thermodynamics by Mayer in his letter^[4] dated July 24, 1841. Max Planck used "quanta" to mean "quanta of matter and electricity",^[5] gas, and heat.^[6] In 1905, in response to Planck's work and the experimental work of Lenard (who explained his results by using the term "quanta of electricity"), Albert Einstein suggested that radiation existed in spatially localized packets which he called "quanta of light" ("Lichtquanta").^[7]

The concept of quantization of radiation was discovered in 1900 by Max Planck, who had been trying to understand the emission of radiation from heated objects, known as black-body radiation. By assuming that energy can only be absorbed or released in tiny, differential, discrete packets he called "bundles" or "energy elements",^[8] Planck accounted for the fact that certain objects change colour when heated.^[9] On December 14, 1900, Planck reported his revolutionary findings to the German Physical Society, and introduced the idea of quantization for the first time as a part of his research on black-body radiation.^[10] As a result of his experiments, Planck deduced the numerical value of h, known as the Planck constant, and could also report a more precise value for the Avogadro–Loschmidt number, the number of real molecules in a mole and the unit of electrical charge, to the German Physical Society. After his theory was validated, Planck was awarded the Nobel Prize in Physics in 1918 for his discovery.

Beyond electromagnetic radiation

While quantization was first discovered in electromagnetic radiation, it describes a fundamental aspect of energy not just restricted to photons.^[11] In the attempt to bring experiment into agreement with theory, Max Planck postulated that electromagnetic energy is absorbed or emitted in discrete packets, or quanta.^[12]

References

^ Wiener, N. (1966). Differential Space, Quantum Systems, and Prediction. Cambridge: The Massachusetts Institute of Technology Press
^ E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
^ E. Helmholtz, Robert Mayer's Priorität [1] (German)
^ Herrmann,A. Weltreich der Physik, GNT-Verlag (1991) [2] (German)
^ Planck, M. (1901). "Ueber die Elementarquanta der Materie und der Elektricität". Annalen der Physik (in German) 309 (3): 564–566. Bibcode:1901AnP...309..564P. doi:10.1002/andp.19013090311.
^ Planck, Max (1883). "Ueber das thermodynamische Gleichgewicht von Gasgemengen". Annalen der Physik (in German) 255 (6): 358. Bibcode:1883AnP...255..358P. doi:10.1002/andp.18832550612.
^ Einstein, A. (1905). "Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt" (PDF). Annalen der Physik (in German) 17 (6): 132–148. Bibcode:1905AnP...322..132E. doi:10.1002/andp.19053220607. . A partial English translation is available from Wikisource.
^ Max Planck (1901). "Ueber das Gesetz der Energieverteilung im Normalspectrum (On the Law of Distribution of Energy in the Normal Spectrum)". Annalen der Physik 309 (3): 553. Bibcode:1901AnP...309..553P. doi:10.1002/andp.19013090310. Archived from the original on 2008-04-18.
^ Brown, T., LeMay, H., Bursten, B. (2008). Chemistry: The Central Science Upper Saddle River, NJ: Pearson Education ISBN 0-13-600617-5
^ Klein, Martin J. (1961). "Max Planck and the beginnings of the quantum theory". Archive for History of Exact Sciences 1 (5): 459. doi:10.1007/BF00327765.
^ Melville, K. (2005, February 11). Real-World Quantum Effects Demonstrated
^ Modern Applied Physics-Tippens third edition; McGraw-Hill.

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English Journal

A master equation for a two-sided optical cavity.

Barlow TM1, Bennett R1, Beige A1.
Journal of modern optics.J Mod Opt.2015 Dec 8;62(sup2):S11-S20. Epub 2015 Jan 21.
Quantum optical systems, like trapped ions, are routinely described by master equations. The purpose of this paper is to introduce a master equation for two-sided optical cavities with spontaneous photon emission. To do so, we use the same notion of photons as in linear optics scattering theory and
PMID 25892851

CdSe/ZnS Quantum Dots-Labeled Mesenchymal Stem Cells for Targeted Fluorescence Imaging of Pancreas Tissues and Therapy of Type 1 Diabetic Rats.

Liu H1, Tang W, Li C, Lv P, Wang Z, Liu Y, Zhang C, Bao Y, Chen H, Meng X, Song Y, Xia X, Pan F, Cui D, Shi Y.
Nanoscale research letters.Nanoscale Res Lett.2015 Dec;10(1):959. doi: 10.1186/s11671-015-0959-3. Epub 2015 Jun 13.
Mesenchymal stem cells (MSCs) have been used for therapy of type 1 diabetes mellitus. However, the in vivo distribution and therapeutic effects of transplanted MSCs are not clarified well. Herein, we reported that CdSe/ZnS quantum dots-labeled MSCs were prepared for targeted fluorescence imaging and
PMID 26078050

Electronic Structure and Carrier Mobilities of Arsenene and Antimonene Nanoribbons: A First-Principle Study.

Wang Y1, Ding Y.
Nanoscale research letters.Nanoscale Res Lett.2015 Dec;10(1):955. doi: 10.1186/s11671-015-0955-7. Epub 2015 Jun 4.
Arsenene and antimonene, i.e. two-dimensional (2D) As and Sb monolayers, are the recently proposed cousins of phosphorene (Angew. Chem. Int. Ed., 54, 3112 (2015)). Through first-principle calculations, we systematically investigate electronic and transport properties of the corresponding As and Sb n
PMID 26058516

Near-Infrared Emitting AgInTe2 and Zn-Ag-In-Te Colloidal Nanocrystals.

Langevin MA1, Pons T, Ritcey AM, Allen CN.
Nanoscale research letters.Nanoscale Res Lett.2015 Dec;10(1):951. doi: 10.1186/s11671-015-0951-y. Epub 2015 Jun 5.
The synthesis of AgInTe2 nanocrystals emitting between 1095 and 1160 nm is presented. Evolution of the Ag:In:Te ratio shows progressive incorporation of In(3+) in Ag2Te, leading to the formation of orthorhombic AgInTe2. When zinc is added to the synthesis, the photoluminescence quantum yield reaches
PMID 26058512