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What is quantum mechanics, and what is old quantum theory?

Physics-3871216 1920

The 1927 Solvay Conference in Brussels.

Quantum mechanics (QM), also called quantum physics or quantum theory, is the branch of physics that describes physical phenomena at microscopic scales. It departs from classical mechanics most clearly in the quantum realm of atomic and subatomic distances, where matter and radiation display both wave-like and particle-like behavior. Quantum mechanics provides the mathematical framework for describing the behavior and interactions of energy and matter under such conditions.

In most contexts, the phrase quantum mechanics refers to the non-relativistic theory. More advanced theories that incorporate relativity, such as quantum field theory, are usually treated separately.

Old quantum theory refers to the collection of ideas developed between about 1900 and 1925, before the modern formulation of quantum mechanics. Although old quantum theory was never fully self-consistent, it produced a number of important successes and clearly showed that the classical Newtonian picture of matter was incomplete. In 1926, Erwin Schrödinger introduced a wave equation that reproduced the successes of old quantum theory while avoiding many of its ambiguities. At about the same time, matrix mechanics was developed by Heisenberg, Born, and Jordan. The two formulations were later shown to be mathematically equivalent.

This article focuses mainly on the more intuitive wave-mechanical formulation.

When is a system in the quantum realm?

Classical physics is usually concerned with everyday conditions: speeds much lower than the speed of light, and sizes much greater than atoms. Modern physics is often concerned with high velocities and very small distances.

The central constant of quantum mechanics is the Planck constant, denoted by $h$. This constant has no analogue in Newtonian mechanics. Its units may be written either as energy multiplied by time, or as momentum multiplied by distance; both are units of action.

A system is likely to display quantum behavior when a relevant mass, length scale, or momentum becomes small enough that the action of the system is comparable to $h$. In practice, this often occurs in the following situations:

• Small mass. Electrons are much less massive than protons or neutrons. For this reason, the electrons in an atom must be treated quantum mechanically, while the nucleus can often be approximated as a fixed classical source of electric force.

• Small spatial confinement. A particle confined to a very small region, such as an electron inside an atom of typical size $10^{-10}$ m, exhibits pronounced quantum effects.

• Very low temperature. At extremely low temperatures, atomic motion becomes slow enough that quantum effects become macroscopically important.

A fourth important case arises in high-energy collisions, where particles may be created or destroyed. That subject belongs mainly to particle physics and quantum field theory, and is mostly beyond the scope of this article.

Timeline

• 1900 – Max Planck introduces energy quanta in order to reproduce the observed spectrum of black-body radiation.
• 1905 – Albert Einstein applies Planck's hypothesis to explain the photoelectric effect, strengthening the case that light has particle-like properties.
• 1909 – G. I. Taylor shows that even extremely feeble light can produce an interference pattern, suggesting that individual photons can interfere with themselves.
• 1913 – Niels Bohr proposes the Bohr model of the hydrogen atom.
• 1923 – Arthur Compton explains the scattering of X-rays by electrons, demonstrating the particle-like momentum of light.
• 1924 – Louis de Broglie proposes that matter has wave-like properties.
• 1926 – Erwin Schrödinger formulates the Schrödinger equation.
• 1926 – Max Born interprets the wavefunction probabilistically.
• 1927 – The Davisson–Germer experiment confirms electron diffraction.
• 1927 – Werner Heisenberg formulates the uncertainty principle.
• 1935 – Schrödinger introduces Schrödinger's cat, and the EPR paradox is formulated.
• 1947 – The Lamb shift is measured, helping establish the correctness of quantum electrodynamics.
• 1948 – Quantum electrodynamics is developed by Feynman, Schwinger, and Tomonaga.
• 1957 – Hugh Everett III proposes the many-worlds interpretation.
• 1964 – John Bell derives Bell's theorem.
• 1981 – Richard Feynman proposes quantum simulation as a route toward quantum computation.
• 1984 – The BB84 protocol introduces quantum cryptography.
• 1994 – Peter Shor discovers Shor's algorithm.
• 1995 – Quantum error correction is developed.
• 1998 – Experimental quantum teleportation is demonstrated.
• 2001 – A small-scale experimental implementation of Shor's algorithm is reported.
• 2015 – Loophole-free Bell tests are performed.
• 2019 – Google claims a demonstration of quantum supremacy.
• 2022 – The Nobel Prize in Physics is awarded to Alain Aspect, John Clauser, and Anton Zeilinger for experiments on entangled photons, Bell inequalities, and quantum information science.
• 2023 – Progress is reported toward fault-tolerant quantum computing.
• 2024 – Work continues on larger and more reliable quantum processors and improved error correction.
• 2025 – Research continues on fault-tolerant quantum computing and quantum networking.

Black-body radiation 1900

A black body.

Old quantum theory effectively began in 1900, when Max Planck derived a formula that accurately reproduced the observed spectrum of black-body radiation. In doing so, he assumed that energy is emitted and absorbed only in discrete amounts, or quanta.

In Planck's model, the constant $h$ appears in the relation between the energy $E$ and frequency $f$ of radiation:

$E=hf$

(Eq. 1)

This is now called the Planck relation. Planck himself did not initially interpret this as meaning that light literally consisted of particles. He regarded quantization as a property of the interaction between matter and radiation rather than of the radiation field itself.

Equation (1) shows that energy is directly proportional to frequency. Since $c=f\lambda$, higher-frequency radiation has shorter wavelength and greater energy.

Photoelectric effect 1905

A schematic illustration of the photoelectric effect.

In 1905 Albert Einstein explained the photoelectric effect, in which electrons are emitted from a material illuminated by light. He proposed that light behaves, in certain experiments, as if it were made of localized packets of energy now called photons.

According to Einstein's interpretation, each photon has energy $E=hf$ and transfers that energy to a single electron. This explains why increasing the light intensity increases the number of emitted electrons, while increasing the light frequency increases their maximum kinetic energy.

Einstein's work strongly reinforced the idea that electromagnetic radiation has both wave-like and particle-like properties.

More links on the photoelectric effect

• http://phet.colorado.edu/en/simulation/photoelectric
• https://en.wikiversity.org/wiki/Photoelectric_Effect_for_Beginners

Taylor makes things spooky with very dim light in 1909

Interference occurs even when particles pass one at a time.

Young's original drawing was used to predict the diffraction pattern for a given wavelength.

Light interferes with itself after passing through two slits.

At the beginning of the nineteenth century, Thomas Young argued that light behaves as a wave and supported this view with his famous double-slit experiment. Interference and diffraction are classic wave phenomena and were taken as strong evidence against Newton's corpuscular theory of light.

About a century later, G. I. Taylor repeated the experiment with light so weak that only one photon at a time was likely to be involved. Even under such conditions, an interference pattern gradually appeared.

This is one of the earliest and most striking indications that a single quantum object can behave in a wave-like manner. Similar experiments have since been performed with electrons, atoms, and even large molecules.

Bohr-Rutherford model 1913

Here $E=E_2-E_1$ is the energy lost when an electron drops from a higher orbit to a lower one.

In 1913 Niels Bohr proposed a model of the hydrogen atom in which electrons move in circular orbits around the nucleus, but only certain orbits are allowed. The model is now known to be incomplete, yet it was an important milestone because it successfully explained the observed spectral lines of hydrogen.

In modern language, one may summarize the Bohr picture using standing-wave ideas:

$n\lambda =2\pi r(n=1,2,3,\cdots )$

(Eq. 2)

together with the de Broglie relation

$\lambda =\frac{h}{p}$

(Eq. 3)

where $p=mv$ in the nonrelativistic approximation.

Although Bohr did not originally formulate his theory in these terms, the standing-wave picture captures the idea that only certain orbits are compatible with a stable wave pattern. The energies of those allowed states are quantized, and radiation is emitted when the atom transitions between them.

Compton effect 1923

Compton scattering is somewhat analogous to a collision, though the correct treatment is relativistic.

A photon of wavelength $\lambda$ scatters from an electron and emerges with wavelength ${\lambda }^{\prime }$.

In 1923 Arthur Compton showed that X-rays scattering from electrons behave as if the radiation carries momentum. The wavelength of the scattered radiation changes in a way that can be explained only if the incoming light is treated as a particle-like object with momentum.

For a photon, the momentum is not $mv$ but rather $p=hf/c$. The Compton effect therefore provided strong evidence that light possesses not only energy but also momentum in discrete quanta.

de Broglie waves 1924

A traveling wave suggests how wave-like structure may be associated with a moving particle.

In 1924 Louis de Broglie proposed that the wave-particle duality of light should be extended to matter. If light, long understood as a wave, can also behave like a particle, then perhaps matter particles can also have wave-like properties.

Today the de Broglie relations are usually written as

$p=\hslash k$

$E=\hslash \omega$

where $\hslash =h/2\pi$, $k=2\pi /\lambda$, and $\omega =2\pi f$. These relations connect momentum with wavelength and energy with frequency.

De Broglie's proposal was bold, but it proved extraordinarily fruitful. It suggested that the quantized orbits of Bohr might eventually be replaced by a more general wave theory of matter.

Schrödinger wave equation 1926

Examples of wavefunctions for the quantum harmonic oscillator.

A simple wavepacket moving through space.

In 1926 Erwin Schrödinger introduced the wave equation that now bears his name:

$i\hslash \frac{\partial }{\partial t}\mathrm{\Psi }(\mathbf{𝐫},t)=[-\frac{{\hslash }^2}{2m}{\mathrm{\nabla }}^2+V(\mathbf{𝐫},t)]\mathrm{\Psi }(\mathbf{𝐫},t)$

(Eq. 4)

This equation describes how the wavefunction $\mathrm{\Psi }$ evolves in time. It is deterministic in the sense that if the initial wavefunction is known, the later wavefunction is determined.

Schrödinger's equation reproduced the observed energy levels of the hydrogen atom and provided a general framework for quantum theory. At about the same time, matrix mechanics was developed independently and later shown to be equivalent.

What is the nature of the wavefunction?

Schrödinger's equation predicts how the wavefunction changes, but it does not by itself say what the wavefunction is. Schrödinger initially hoped that $|\mathrm{\Psi }{|}^2$ might represent a kind of physical charge density. Max Born instead proposed the interpretation that $|\mathrm{\Psi }{|}^2$ is a probability density.

This probabilistic interpretation became central to modern quantum mechanics. It means that the wavefunction does not directly tell us where a particle is, but rather the probabilities for the outcomes of measurements.

Davisson–Germer's accidental diffraction of electrons 1927

Davisson (left) and Germer (right).

While studying electron scattering from nickel, Davisson and Germer observed a diffraction pattern caused by the crystal structure of the target. Their experiment provided direct confirmation that electrons have wave-like properties, as predicted by de Broglie.

This result was one of the key experimental supports for wave mechanics.

Heisenberg's uncertainty principle 1927

A narrow slit produces strong diffraction.

A wider slit produces less spreading.

Werner Heisenberg realized that the act of measurement is not a passive process in quantum mechanics. The more precisely one tries to localize a particle, the less precisely one can know its momentum.

A simple way to understand this is through diffraction. If a particle passes through a narrow slit, its position becomes better defined, but the emerging wave spreads out more strongly. This implies greater uncertainty in momentum. The result is expressed mathematically by

${\sigma }_x{\sigma }_p\ge \frac{\hslash }{2}$

(Eq. 5)

where ${\sigma }_x$ is the uncertainty in position and ${\sigma }_p$ is the uncertainty in momentum.

Copenhagen interpretation

Wavepackets can become delocalized. In the probabilistic interpretation, what is spread out is the probability amplitude.

The Copenhagen interpretation treats the wavefunction as a tool for calculating probabilities. In this view:

1. $|\mathrm{\Psi }{|}^2\mathrm{\Delta }V$ gives the probability of finding the particle in a small volume $\mathrm{\Delta }V$.
2. A superposition of energy eigenstates implies a probability distribution over possible measurement outcomes.
3. A measurement can change the state, producing what is traditionally called wavefunction collapse.

These ideas remain conceptually controversial, but they form the standard operational framework used in most practical applications of quantum mechanics.

Schrödinger's cat 1935

A cat in a sealed box becomes the subject of a famous thought experiment about superposition and measurement.

In 1935 Schrödinger proposed his famous cat thought experiment in order to dramatize the interpretive difficulties of quantum mechanics. If a microscopic quantum event determines whether a poison flask is broken, then the standard quantum description seems to imply that the cat is in a superposition of "alive" and "dead" until a measurement is made.

The thought experiment was intended not as a defense of that conclusion, but as a criticism of taking the formalism too literally at macroscopic scales.

Developments

• 1964 – John Stewart Bell derives Bell's theorem.
• 1982 – Alain Aspect and collaborators perform influential experiments testing Bell inequalities.
• 2010 – Andrew Cleland and collaborators place a mesoscopic mechanical system into a quantum superposition-like state.

Lamb shift 1947

Hydrogen energy levels including fine structure and the Lamb shift.

In 1947 Willis Lamb and Robert Retherford measured a small shift in hydrogen energy levels now known as the Lamb shift. This result showed that a simple relativistic wave equation for the electron was not sufficient. The interaction of the electron with the quantized electromagnetic field had to be taken into account.

The Lamb shift became one of the early triumphs of quantum electrodynamics.

Quantum electrodynamics 1948

A Feynman diagram, a standard tool in quantum field theory.

By the late 1940s, Richard Feynman, Julian Schwinger, and Sin-Itiro Tomonaga had developed quantum electrodynamics (QED). QED describes the interaction of light and charged matter and remains one of the most accurate physical theories ever constructed.

Many-worlds interpretation 1957

The cat paradox as viewed in the many-worlds interpretation.

In 1957 Hugh Everett III proposed the many-worlds interpretation of quantum mechanics. In this interpretation, the wavefunction never collapses. Instead, measurement correlates observer and system, giving rise to effectively separate branches corresponding to different outcomes.

Whether this interpretation is the best one remains debated, but it permanently influenced discussions of quantum foundations.

Bell's theorem 1964

A schematic Bell-test setup.

In 1964 John Bell showed that no theory based on local hidden variables can reproduce all the predictions of quantum mechanics. Bell's theorem turned a philosophical question into an experimentally testable one.

Quantum simulation 1981

A qubit may be represented on a Bloch sphere.

In 1981 Richard Feynman argued that quantum systems are difficult to simulate efficiently on classical computers and suggested using one quantum system to simulate another. This idea helped launch the field of quantum computing.

Quantum cryptography 1984

An optical implementation of the BB84 protocol.

In 1984 Charles Bennett and Gilles Brassard proposed the BB84 protocol. BB84 showed that the laws of quantum mechanics can be used to distribute a secret key in such a way that eavesdropping becomes detectable.

Shor's algorithm 1994

Classical asymmetric cryptography may be threatened by large-scale quantum computation.

In 1994 Peter Shor discovered Shor's algorithm, which can factor integers efficiently on a quantum computer. This dramatically increased interest in quantum computing because many classical cryptographic systems rely on the presumed difficulty of factoring.

Quantum error correction 1995

File:Shor code.svg

A quantum circuit for the Shor code.

Quantum states are extremely fragile, yet in 1995 researchers showed that quantum information can nevertheless be protected using quantum error correction. This was a decisive conceptual breakthrough for quantum computing.

Quantum teleportation 1998

In 1998 early experimental demonstrations of quantum teleportation were achieved. Quantum teleportation transfers a quantum state from one system to another using entanglement and classical communication; it does not transport matter itself.

Experimental Shor demonstration 2001

In 2001 a small-scale experimental implementation of Shor's algorithm was reported. Although the example was tiny, it showed that nontrivial quantum algorithms could be demonstrated in the laboratory.

Loophole-free Bell tests 2015

A schematic two-channel Bell test.

In 2015 several groups reported loophole-free Bell tests. These experiments closed the major loopholes that had left room for alternative explanations in earlier Bell tests, and they strongly supported the nonclassical correlations predicted by quantum mechanics.

Quantum field theory and particle physics

Modern particle physics is described by quantum field theory, in which particles are excitations of underlying fields. A prominent example is the Higgs boson, discovered in 2012, associated with the Higgs field that gives mass to other particles.

These developments lie beyond non-relativistic quantum mechanics but represent a natural extension of quantum theory to relativistic systems.

Quantum supremacy claim 2019

In 2019 Google announced that a quantum processor had completed a specific computational task faster than a known classical alternative and described the result as quantum supremacy. Although the term and the practical importance of the benchmark were debated, the announcement marked a major public milestone in quantum computing.

Entanglement Nobel Prize 2022

Entanglement has moved from philosophical puzzle to experimental resource.

In 2022 the Nobel Prize in Physics was awarded to Alain Aspect, John Clauser, and Anton Zeilinger for experiments with entangled photons, for establishing the violation of Bell inequalities, and for pioneering quantum information science.

Fault-tolerant progress 2023

Illustration of different quantum computing paradigms

In 2023 further progress was reported toward fault-tolerant quantum computing, especially in the protection of logical qubits against errors.

Scalable processors and error correction 2024

In 2024 work continued on larger quantum processors, improved calibration, and better implementations of error-correcting codes.

Quantum computing and networking 2025

In 2025 research continued on fault-tolerant quantum computing and on quantum networking, including the distribution of entanglement across larger systems.

Index

Core theory Foundations Conceptual and interpretations Mathematical structure and systems Atomic and spectroscopy Wavefunctions and modes Quantum dynamics and evolution Measurement and information Quantum information and computing

Applications and extensions Quantum optics and experiments Open quantum systems Quantum field theory Statistical mechanics and kinetic theory Condensed matter and solid-state physics Plasma and fusion physics Timeline Advanced and frontier topics

Quantum Book II

Matter by scale

Quantum Book III

Methods and tools

Quantum Book IV

Data Analysis Techniques

Full contents

Foundations



1. Physics:Quantum basics
2. Physics:Quantum Postulates
3. Physics:Quantum Hilbert space
4. Physics:Quantum Observables and operators
5. Physics:Quantum mechanics
6. Physics:Quantum mechanics measurements
7. Physics:Quantum state
8. Physics:Quantum system
9. Physics:Quantum superposition
10. Physics:Quantum probability
11. Physics:Quantum Mathematical Foundations of Quantum Theory

Conceptual and interpretations



12. Physics:Quantum Interpretations of quantum mechanics
13. Physics:Quantum Wave–particle duality
14. Physics:Quantum Complementarity principle
15. Physics:Quantum Uncertainty principle
16. Physics:Quantum Measurement problem
17. Physics:Quantum Bell's theorem
18. Physics:Quantum Hidden variable theory
19. Physics:Quantum nonlocality
20. Physics:Quantum contextuality
21. Physics:Quantum Darwinism
22. Physics:Quantum A Spooky Action at a Distance
23. Physics:Quantum A Walk Through the Universe
24. Physics:Quantum The Secret of Cohesion and How Waves Hold Matter Together
25. Physics:Quantum measurement problem

Mathematical structure and systems



26. Physics:Quantum Density matrix
27. Physics:Quantum Exactly solvable quantum systems
28. Physics:Quantum Formulas Collection
29. Physics:Quantum A Matter Of Size
30. Physics:Quantum Symmetry in quantum mechanics
31. Physics:Quantum Angular momentum operator
32. Physics:Quantum Runge–Lenz vector
33. Physics:Quantum Approximation Methods
34. Physics:Quantum Matter Elements and Particles
35. Physics:Quantum Dirac equation
36. Physics:Quantum Klein–Gordon equation
37. Physics:Quantum pendulum
38. Physics:Quantum configuration space

Atomic and spectroscopy



Quantum atomic structure and spectroscopy: orbitals, energy levels, and emission and absorption spectra.

39. Physics:Quantum Atomic structure and spectroscopy
40. Physics:Quantum Hydrogen atom
41. Physics:Quantum number
42. Physics:Quantum Multi-electron atoms
43. Physics:Quantum Fine structure
44. Physics:Quantum Hyperfine structure
45. Physics:Quantum Isotopic shift
46. Physics:Quantum defect
47. Physics:Quantum Zeeman effect
48. Physics:Quantum Stark effect
49. Physics:Quantum Spectral lines and series
50. Physics:Quantum Selection rules
51. Physics:Quantum Fermi's golden rule
52. Physics:Quantum beats

Wavefunctions and modes



A quantum wavefunction showing probability amplitude in space; the square of its magnitude gives the probability density.

53. Physics:Quantum Wavefunction
54. Physics:Quantum Superposition principle
55. Physics:Quantum Eigenstates and eigenvalues
56. Physics:Quantum Boundary conditions and quantization
57. Physics:Quantum Standing waves and modes
58. Physics:Quantum Normal modes and field quantization
59. Physics:Number of independent spatial modes in a spherical volume
60. Physics:Quantum Density of states
61. Physics:Quantum carpet

Quantum dynamics and evolution



62. Physics:Quantum Time evolution
63. Physics:Quantum Schrödinger equation
64. Physics:Quantum Time-dependent Schrödinger equation
65. Physics:Quantum Stationary states
66. Physics:Quantum Perturbation theory
67. Physics:Quantum Time-dependent perturbation theory
68. Physics:Quantum Adiabatic theorem
69. Physics:Quantum Scattering theory
70. Physics:Quantum S-matrix
71. Physics:Quantum tunnelling
72. Physics:Quantum speed limit
73. Physics:Quantum revival
74. Physics:Quantum reflection
75. Physics:Quantum oscillations
76. Physics:Quantum jump
77. Physics:Quantum boomerang effect
78. Physics:Quantum chaos

Measurement and information



79. Physics:Quantum Measurement theory
80. Physics:Quantum Measurement operators
81. Physics:Quantum Projective measurement
82. Physics:Quantum POVM
83. Physics:Quantum Weak measurement
84. Physics:Quantum Measurement collapse
85. Physics:Quantum entanglement
86. Physics:Quantum Zeno effect
87. Physics:Quantum limit

Quantum information and computing



88. Physics:Quantum information theory
89. Physics:Quantum Qubit
90. Physics:Quantum Entanglement
91. Physics:Quantum Gates and circuits
92. Physics:Quantum Computing Algorithms in the NISQ Era
93. Physics:Quantum Noisy Qubits
94. Physics:Quantum random access code
95. Physics:Quantum pseudo-telepathy
96. Physics:Quantum network
97. Physics:Quantum money

Quantum optics and experiments



Experimental quantum physics: qubits, dilution refrigerators, quantum communication, and laboratory systems.

98. Physics:Quantum Nonlinear King plot anomaly in calcium isotope spectroscopy
99. Physics:Quantum optics beam splitter experiments
100. Physics:Quantum Ultra fast lasers
101. Physics:Quantum Experimental quantum physics
102. Physics:Quantum optics
103. Template:Quantum optics operators

Open quantum systems



104. Physics:Quantum Open systems
105. Physics:Quantum Master equation
106. Physics:Quantum Lindblad equation
107. Physics:Quantum Decoherence
108. Physics:Quantum dissipation
109. Physics:Quantum Markov semigroup
110. Physics:Quantum Markovian dynamics
111. Physics:Quantum Non-Markovian dynamics
112. Physics:Quantum Trajectories

Quantum field theory



Structural dependency map of quantum field theory.

113. Physics:Quantum field theory (QFT) basics
114. Physics:Quantum field theory (QFT) core
115. Physics:Quantum Fields and Particles
116. Physics:Quantum Second quantization
117. Physics:Quantum Harmonic Oscillator field modes
118. Physics:Quantum Creation and annihilation operators
119. Physics:Quantum vacuum fluctuations
120. Physics:Quantum Propagators in quantum field theory
121. Physics:Quantum Feynman diagrams
122. Physics:Quantum Path integral formulation
123. Physics:Quantum Renormalization in field theory
124. Physics:Quantum Renormalization group
125. Physics:Quantum Field Theory Gauge symmetry
126. Physics:Quantum Non-Abelian gauge theory
127. Physics:Quantum Electrodynamics (QED)
128. Physics:Quantum chromodynamics (QCD)
129. Physics:Quantum Electroweak theory
130. Physics:Quantum Standard Model
131. Physics:Quantum triviality
132. Physics:Quantum confinement problem

Statistical mechanics and kinetic theory



133. Physics:Quantum Statistical mechanics
134. Physics:Quantum Partition function
135. Physics:Quantum Distribution functions
136. Physics:Quantum Liouville equation
137. Physics:Quantum Kinetic theory
138. Physics:Quantum Boltzmann equation
139. Physics:Quantum BBGKY hierarchy
140. Physics:Quantum Relaxation and thermalization
141. Physics:Quantum Thermodynamics

Condensed matter and solid-state physics



142. Physics:Quantum Band structure
143. Physics:Quantum Fermi surfaces
144. Physics:Quantum Semiconductor physics
145. Physics:Quantum Phonons
146. Physics:Quantum Electron-phonon interaction
147. Physics:Quantum Superconductivity
148. Physics:Quantum Topological phases of matter
149. Physics:Quantum well
150. Physics:Quantum spin liquid
151. Physics:Quantum spin Hall effect
152. Physics:Quantum phase transition
153. Physics:Quantum critical point
154. Physics:Quantum dot

Plasma and fusion physics



Conceptual illustration of plasma physics in a fusion context, showing magnetically confined ionized gas in a tokamak and the collective behavior governed by electromagnetic fields and transport processes.

155. Physics:Quantum Fusion reactions and Lawson criterion
156. Physics:Quantum Plasma (fusion context)
157. Physics:Quantum Magnetic confinement fusion
158. Physics:Quantum Inertial confinement fusion
159. Physics:Quantum Plasma instabilities and turbulence
160. Physics:Quantum Tokamak core plasma
161. Physics:Quantum Tokamak edge physics and recycling asymmetries
162. Physics:Quantum Stellarator

Timeline



163. Physics:Quantum mechanics/Timeline
164. Physics:Quantum mechanics/Timeline/Pre-quantum era
165. Physics:Quantum mechanics/Timeline/Old quantum theory
166. Physics:Quantum mechanics/Timeline/Modern quantum mechanics
167. Physics:Quantum mechanics/Timeline/Quantum field theory era
168. Physics:Quantum mechanics/Timeline/Quantum information era
169. Physics:Quantum mechanics/Timeline/Quantum technology era
170. Physics:Quantum mechanics/Timeline/Quiz

Advanced and frontier topics



171. Physics:Quantum topology
172. Physics:Quantum battery
173. Physics:Quantum Supersymmetry
174. Physics:Quantum Black hole thermodynamics
175. Physics:Quantum Holographic principle
176. Physics:Quantum gravity
177. Physics:Quantum De Sitter invariant special relativity
178. Physics:Quantum Doubly special relativity
179. Physics:Quantum arithmetic geometry
180. Physics:Quantum unsolved problems
181. Physics:Quantum Yang-Mills mass gap
182. Physics:Quantum gravity problem
183. Physics:Quantum black hole information paradox
184. Physics:Quantum dark matter problem
185. Physics:Quantum neutrino mass problem
186. Physics:Quantum matter-antimatter asymmetry problem

Physics:Quantum_mechanics/Timeline/Quiz/

See the subpage for a quiz on this topic.

References and Endnotes

• Most of the material was adapted from Wikipedia

Author: Harold Foppele