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Saturday, September 14, 2019

Principles of quantum mechanics

This post is list of collection of principles in quantum mechanics. There are 52 quotes from Wikipedia divided into 22 sections. The sections are ordered chronologically according to the date of their discovery. License: CC BY-SA 3.0


1. Quanta

2. Planck constant

3. Atomic orbitals

4. Bohr model

5. Wave-particle duality

6. Quantum spin

7. Pauli exclusion principle

8. Matrix mechanics

9. Schrodinger equation

10. Born rule

11. Uncertainty principle

12. Quantum field theory

13. Quantum electrodynamics

14. Quantum tunneling

15. Dirac equation

16. Antimatter

17. Quantum entanglement

18. Feynman diagrams

19. Virtual particles

20. Path integral formulation

21. Quantum foam

22. Quantum chromodynamics



1. Quanta (1900)


"In physics, a quantum (plural: quanta) is the minimum amount of any physical entity (physical property) involved in an interaction... This means that the magnitude of the physical property can take on only discrete values consisting of integer multiples of one quantum." (Wikipedia: Quantum, 8.6.21 UTC 20:33)


"A photon is a single quantum of light (or of any other form of electromagnetic radiation). Similarly, the energy of an electron bound within an atom is quantized and can exist only in certain discrete values." (Wikipedia: Quantum, 8.6.21 UTC 20:33)


"The concept of quantization 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." (Wikipedia: Quantum, 8.6.21 UTC 20:33)


2. Planck constant (1900)


"The Planck constant is a physical constant denoted h... A photon's energy is equal to its frequency multiplied by the Planck constant." (Wikipedia: Planck constant, 8.9.21 UTC 07:24)


3. Atomic orbitals (1904)


"The term atomic orbital may also refer to the physical region or space where the electron can be calculated to be present, as defined by the particular mathematical form of the orbital." (Wikipedia: Atomic orbital, 8.15.21 UTC 21:31)


"Each orbital can be occupied by a maximum of two electrons..." (Wikipedia: Atomic orbital, 8.15.21 UTC 21:31)


"The repeating periodicity of the blocks of 2, 6, 10 and 14 elements within sections of the periodic table arises naturally from the total number of electrons that occupy a complete set of s, p, d and f atomic orbitals, respectively..." (Wikipedia: Atomic orbital, 8.15.21 UTC 21:31)


4. Bohr model (1913)


"In atomic physics, the Rutherford-Bohr model presented by Niels Bohr and Ernest Rutherford in 1913, is a system consisting of a small, dense nucleus surrounded by revolving electrons..." (Wikipedia: Bohr model, 8.16.21 UTC 04:15)


"The electron is able to revolve in certain stable orbits around the nucleus without radiating any energy..." (Wikipedia: Bohr model, 8.16.21 UTC 04:15)


"Electrons can only gain and lose energy by jumping from one allowed orbit to another, absorbing or emitting electromagnetic radiation..." (Wikipedia: Bohr model, 8.16.21 UTC 04:15)


5. Wave-particle duality (1924)


"Wave-particle duality is the concept in quantum mechanics that every particle or quantum entity may be partly described in terms not only of particles but also of waves." (Wikipedia: Wave-particle duality, 8.10.21 UTC 18:46)


"The particle-like behavior is most evident due to phenomena associated with measurement in quantum mechanics. Upon measuring the location of the particle, the particle will be forced into a more localized state..." (Wikipedia: Wave-particle duality, 8.10.21 UTC 18:46)


6. Quantum spin (1924)


"In 1924 Wolfgang Pauli introduced what he called a 'two-valuedness not describable classically' associated with the electron in the outermost shell." (Wikipedia: Spin, 8.17.21 UTC 12:34)


"Spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei." (Wikipedia: Spin, 8.17.21 UTC 12:34)


"All elementary particles of a given kind have the same magnitude of spin angular momentum, though tis direction may change. These are indicated by assigning the particle a spin quantum number." (Wikipedia: Spin, 8.17.21 UTC 12:34)


7. Pauli exclusion principle (1925)


"The Pauli exclusion principle is the quantum mechanical principle which states that two or more identical fermions... cannot occupy the same quantum state within a quantum system simultaneously." (Wikipedia: Pauli exclusion principle, 6.8.21 UTC 10:47)


8. Matrix mechanics (1925)


"Matrix mechanics was the first conceptually autonomous and logically consistent formulation of quantum mechanics... It did so by interpreting the physical properties of particles as matrices that evolve in time. It is equivalent to the Schrodinger wave formulation of quantum mechanics..." (Wikipedia: Matrix mechanics, 6.5.21 UTC 21:42)


"In some contrast to the wave formulation, it produces spectra of (mostly energy) operators by purely algebraic, ladder operator methods." (Wikipedia: Matrix mechanics, 6.5.21 UTC 21:42)


9. Schrodinger equation (1925)


"The Schrodinger equation gives the evolution over time of a wave function, the quantum-mechanical characterization of an isolated physical system." (Wikipedia: Schrodinger equation, 6.6.32 UTC 18:20)


"In the views often grouped together as the Copenhagen interpretation, a system's wave function is a collection of statistical information about that system." (Wikipedia: Schrodinger equation, 6.6.32 UTC 18:20)


10. Born rule (1926)


"The Born rule... is a key postulate of quantum mechanics which gives the probability that a measurement of a quantum system will yield a given result." (Wikipedia: Born rule, 7.5.21 UTC 18:30)


11. Uncertainty principle (1927)


"[The uncertainty principle] states that the more precisely the position of some particle is determined, the less precisely its momentum can be known, and vice versa." (Wikipedia: Uncertainty Principle, 8.17.21 UTC 07:01)


"...the uncertainty principle is inherent in the properties of all wave-like systems, and that it arises in quantum mechanics simply due to the matter wave nature of all quantum objects." (Wikipedia: Uncertainty Principle, 8.17.21 UTC 07:01)


"The uncertainty principle actually states a fundamental property of quantum systems and is not a statement about the observational success of current technology." (Wikipedia: Uncertainty Principle, 8.17.21 UTC 07:01)


12. Quantum field theory (1927)


"...the history of quantum field theory starts with its creation by Paul Dirac, when he attempted to quantize the electromagnetic field in the late 1920's." (Wikipedia: History of quantum field theory, 8.3.21 UTC 17:06)


"Quantum field theory (QFT) treats particles as excited states (also called quanta) of their underlying fields, which are - in a sense - more fundamental than the basic particles." (Wikipedia: Quantum field theory, 8.4.21 UTC 06:07)


13. Quantum electrodynamics (1927)


"Quantum electrodynamics (QED) mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons..." (Wikipedia: Quantum electrodynamics, 5.27.21 UTC 13:21)


"In essence, [QED] describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved." (Wikipedia: Quantum electrodynamics, 5.27.21 UTC 13:21)


14. Quantum tunneling (1927)


"Quantum tunneling is the quantum mechanical phenomenon where a wavefunction can propagate through a potential barrier." (Wikipedia: Quantum tunneling, 7.13.21 UTC 13:11)


"The probability of a given particle's existence on the opposite side of an intervening barrier is non-zero and such particles will appear on the other side with a relative frequency proportional to this probability." (Wikipedia: Quantum tunneling, 7.13.21 UTC 13:11)


15. Dirac equation (1928)


"Dirac's purpose in casting this equation was to explain the behavior of the relativisically moving electron..." (Wikipedia: Dirac equation, 8.11.21 UTC 18:24)


"The wave functions in the Dirac theory are vectors of four complex number (known as bispinors), two of which resemble the Pauli wavefunction in the non-relativistic limit, in contrast to the Schrodinger equation, which described wave functions of only one complex value." (Wikipedia: Dirac equation, 8.11.21 UTC 18:24)


"The equation also implied the existence of a new form of matter, antimatter, previously unsuspected and unobserved..." (Wikipedia: Dirac equation, 8.11.21 UTC 18:24)


16. Antimatter (1928)


"Theoretically, a particle and its anti-particle... have the same mass, but opposite electric charge and other differences in quantum numbers." (Wikipedia: Antimatter, 8.17.21 UTC 21:01)


"Antimatter particles bind with one another to form antimatter, just as ordinary particles bind to form normal matter." (Wikipedia: Antimatter, 8.17.21 UTC 21:01)


"A collision between any particle and its anti-particle partner leads to their mutual annihilation, giving rise to various proportions of intense photons, neutrinos and sometimes less-massive particle-antiparticle pairs." (Wikipedia: Antimatter, 8.17.21 UTC 21:01)


"There is strong evidence that the observable universe is composed almost entirely of ordinary matter, as opposed to an equal mixture of matter and antimatter." (Wikipedia: Antimatter, 8.17.21 UTC 21:01)


17. Quantum entanglement (1935)


"Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated, interact, or share spatial proximity in ways such that the quantum state of each particle cannot be described independently of the state of the others, even when the particles are separated by a large distance." (Wikipedia: Quantum entanglement, 8.7.21 UTC 08:57)


"Entanglement is broken when the entangled particles decohere through interaction with the environment; for example when a measurement is made." (Wikipedia: Quantum entanglement, 8.7.21 UTC 08:57)


18. Feynman diagrams (1948)


"The interaction of sub-atomic particles can be complex and difficult to understand; Feynman diagrams give a simple visualization of what would be an arcane and abstract formula." (Wikipedia: Feynman diagrams, 6.29.21 UTC 12:43)


"The electron in the initial state is represented by a solid line with an arrow indicating spin of the particle.... Virtual photon in the initial and final state is represented by a wavy line." (Wikipedia: Feynman diagrams, 6.29.21 UTC 12:43)


19. Virtual particles (1948)


"Virtual particles are... excitations of the underlying fields, but are 'temporary' in the sense that they appear in calculations of interactions, but never as asymptotic states or indices to the scattering index." (Wikipedia: Virtual particle, 7.19.21 UTC 02:35)


"Virtual particles are often popularly described as coming in pairs, a particle and antiparticles which can be of any kind. These pairs exist for an extremely short time and then mutually annihilate or in some cases the pair may be boosted apart using external energy..." (Wikipedia: Virtual particle, 7.19.21 UTC 02:35)


"Virtual particles do not necessarily carry the same mass as the corresponding real particle, although they always conserve energy and momentum." (Wikipedia: Virtual particle, 7.19.21 UTC 02:35)


20. Path integral formulation (1948)


"The path integral formulation... replaces the classical notion of a single, unique classical trajectory for a system with a sum, or functional integral, over an infinity of quantum-mechanically possible trajectories to compute a quantum amplitude." (Wikipedia: Path integral formulation, 8.12.21 UTC 17:16)


21. Quantum foam (1955)


"Quantum foam (also known as spacetime foam or spacetime bubble) is the quantum fluctuation of spacetime on very small scales due to quantum mechanics." (Wikipedia: Quantum mechanics, 8.2.21 UTC 23:03)


"Wheeler suggested that the Heisenberg uncertainty principle might imply that over sufficiently brief intervals of time, the 'very geometry of spacetime fluctuates'. These fluctuations could be large enough to cause significant departures from the smooth spacetime seen at macroscopic scales, giving spacetime a 'foamy' character." (Wikipedia: Quantum mechanics, 8.2.21 UTC 23:03)


"The large fluctuations characteristic of a spacetime foam would be expected to occur on a length scale on the order of the Planck length." (Wikipedia: Quantum mechanics, 8.2.21 UTC 23:03)


22. Quantum chromodynamics (1973)


"Quantum chromodynamics (QCD) is the theory of the strong interaction between quarks and gluons, the fundamental particles that make up composite hadrons such as the proton, neutron and pion." (Wikipedia: Quantum chromodynamics, 8.17.21 UTC 21:46)


"Gluons are the force carrier of the theory, just as photons are the electromagnetic force in quantum electrodynamics." (Wikipedia: Quantum chromodynamics, 8.17.21 UTC 21:46)


"The QCD analog of electric charge is a property called color... Other than this nomenclature, the quantum parameter 'color' is completely unrelated to everyday, familiar phenomenon of color." (Wikipedia: Quantum chromodynamics, 8.17.21 UTC 21:46)


"The three kinds of charge in QCD are.. red, green and blue." (Wikipedia: Quantum chromodynamics, 8.17.21 UTC 21:46)