Physics:Quantum mechanics/Timeline/Modern quantum mechanics - Revision history

WikiHarold: Restore missing Quantum reference definitions

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	== Origin of the modern theory ==		== Origin of the modern theory ==

	In 1924, de Broglie proposed that particles of matter, such as electrons, possess an associated wavelength. This hypothesis connected the quantization of Bohr orbits with wave behavior and suggested that atomic structure could be understood through standing waves rather than classical planetary motion.<ref name="Whittaker" /> De Broglie's idea was soon supported experimentally by electron diffraction, showing that electrons can behave as waves.		In 1924, de Broglie proposed that particles of matter, such as electrons, possess an associated wavelength. This hypothesis connected the quantization of Bohr orbits with wave behavior and suggested that atomic structure could be understood through standing waves rather than classical planetary motion.<ref name="Whittaker">{{Cite book \|last=Whittaker \|first=Edmund T. \|title=A history of the theories of aether & electricity. 2: The modern theories, 1900–1926 \|date=1989 \|publisher=Dover Publications \|isbn=978-0-486-26126-3 \|edition=Reprint \|location=New York}}</ref> De Broglie's idea was soon supported experimentally by electron diffraction, showing that electrons can behave as waves.

	In 1925, Heisenberg formulated a new quantum theory based only on observable quantities such as spectral-line frequencies and intensities. Born recognized that Heisenberg's calculations could be expressed using matrices, leading to the formulation known as '''matrix mechanics'''.<ref name="Heisenberg1925">{{cite book \|last=Van der Waerden \|first=B. L. \|title=Sources of Quantum Mechanics \|date=1967 \|publisher=Dover Publications \|location=Mineola, New York \|pages=261–276}}</ref>		In 1925, Heisenberg formulated a new quantum theory based only on observable quantities such as spectral-line frequencies and intensities. Born recognized that Heisenberg's calculations could be expressed using matrices, leading to the formulation known as '''matrix mechanics'''.<ref name="Heisenberg1925">{{cite book \|last=Van der Waerden \|first=B. L. \|title=Sources of Quantum Mechanics \|date=1967 \|publisher=Dover Publications \|location=Mineola, New York \|pages=261–276}}</ref>
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	{{#invoke:PhysicsQC\|tocHeadingAndList\|Physics:Quantum basics/See also}}		{{#invoke:PhysicsQC\|tocHeadingAndList\|Physics:Quantum basics/See also}}

	== References ==		= References =
	{{reflist\|3}}		{{reflist\|3}}

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	{{Quantum book backlink\|Timeline}}		{{Quantum book backlink\|Timeline}}
	{{Quantum article nav\|previous=Physics:Quantum mechanics/Timeline/Old quantum theory\|previous label=Timeline: Old quantum theory\|next=Physics:Quantum mechanics/Timeline/Quantum field theory era\|next label=Timeline: Quantum field theory era}}		{{Quantum article nav\|previous=Physics:Quantum mechanics/Timeline/Old quantum theory\|previous label=Timeline: Old quantum theory\|next=Physics:Quantum mechanics/Timeline/Quantum field theory era\|next label=Timeline: Quantum field theory era}}

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	{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}		{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}

	{{Quantum book backlink\|Timeline}}		{{Quantum book backlink\|Timeline}}
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	{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}~~Book I~~		{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}

	{{Quantum book backlink\|Timeline}}		{{Quantum book backlink\|Timeline}}

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	~~~~{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}		{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}Book I

	{{Quantum book backlink\|Timeline}}		{{Quantum book backlink\|Timeline}}

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	{{Quantum book backlink\|Timeline}}		{{Quantum book backlink\|Timeline}}
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	'''Modern quantum mechanics''' in the timeline covers the consolidation and expansion of quantum theory after its foundational formulation. This period includes the refinement of operator methods, scattering theory, quantum electrodynamics, many-body physics, condensed matter applications, and increasingly precise experimental tests.		'''Modern quantum mechanics''' in the timeline covers the consolidation and expansion of quantum theory after its foundational formulation. This period includes the refinement of operator methods, scattering theory, quantum electrodynamics, many-body physics, condensed matter applications, and increasingly precise experimental tests.

	The era also saw quantum mechanics become a working language for chemistry, electronics, lasers, semiconductors, superconductivity, and atomic clocks. In the Quantum Collection timeline, this page links historical developments to the concepts and technologies that shaped contemporary quantum physics.		The era also saw quantum mechanics become a working language for chemistry, electronics, lasers, semiconductors, superconductivity, and atomic clocks. In the Quantum Collection timeline, this page links historical developments to the concepts and technologies that shaped contemporary quantum physics. It also highlights the movement from foundational debates toward mature mathematical tools and laboratory methods. The page is meant to help readers place modern quantum concepts in historical order.
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	{{Quantum book backlink\|Timeline}}		{{Quantum book backlink\|Timeline}}
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	'''~~Timeline:~~ Modern quantum mechanics''' ~~mechanics/Timeline/Modern quantum mechanics is a Book I topic~~ in the ~~Quantum Collection. Key figures in contemporary quantum physics~~ and ~~quantum information (post-1950), including pioneers~~ of quantum ~~computing, entanglement, and modern experiments~~. ~~Modern quantum mechanics is~~ the ~~form~~ of ~~quantum~~ theory ~~developed from about 1925 onward, when the older~~, ~~partly phenomenological~~ quantum ~~rules were replaced by a systematic mathematical theory of states~~, ~~observables, operators, and probabilities. Its creation was one of the central events in the history of modern~~ physics~~. The older quantum theory had introduced quantized energy~~, ~~photons, atomic spectra~~, and ~~the Bohr model, but it lacked a complete mathematical foundation~~. The ~~transition to modern~~ quantum mechanics ~~began with Louis de Broglie's proposal that matter has wave-like properties and was completed through the nearly simultaneous development of matrix mechanics by Werner Heisenberg~~, ~~Max Born~~, ~~and Pascual Jordan~~, and wave mechanics by Erwin Schrödinger. Modern quantum mechanics is the form of quantum theory developed from about 1925 onward, when the older, partly phenomenological quantum rules were replaced by a systematic mathematical theory of states, ~~observables, operators~~, and ~~probabilities~~. ~~Its creation was one of~~ the ~~central events in the history of modern physics. The older quantum theory had introduced quantized energy, photons, atomic spectra, and the Bohr model~~, ~~but it lacked a complete mathematical foundation. The transition~~ to ~~modern quantum mechanics began with Louis de Broglie's proposal that matter has wave-like properties and was completed through~~ the ~~nearly simultaneous development of matrix mechanics by Werner Heisenberg, Max Born, and Pascual Jordan,~~ and ~~wave mechanics by Erwin Schrödinger. In 1924, de Broglie proposed~~ that ~~particles of matter, such as electrons, possess an associated wavelength~~.		'''Modern quantum mechanics''' in the timeline covers the consolidation and expansion of quantum theory after its foundational formulation. This period includes the refinement of operator methods, scattering theory, quantum electrodynamics, many-body physics, condensed matter applications, and increasingly precise experimental tests.

			The era also saw quantum mechanics become a working language for chemistry, electronics, lasers, semiconductors, superconductivity, and atomic clocks. In the Quantum Collection timeline, this page links historical developments to the concepts and technologies that shaped contemporary quantum physics.
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	{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}		{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}

	{{Quantum book backlink\|Timeline}}		{{Quantum book backlink\|Timeline}}
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	<div style="flex:1; line-height:1.45; color:#006b45; column-count:2; column-gap:32px; column-rule:1px solid #b8d8c8;">		<div style="flex:1; line-height:1.45; color:#006b45; column-count:2; column-gap:32px; column-rule:1px solid #b8d8c8;">
	'''mechanics/Timeline/Modern quantum mechanics~~'''~~ is a Book I topic in the Quantum Collection. Key figures in contemporary quantum physics and quantum information (post-1950), including pioneers of quantum computing, entanglement, and modern experiments. Modern quantum mechanics is the form of quantum theory developed from about 1925 onward, when the older, partly phenomenological quantum rules were replaced by a systematic mathematical theory of states, observables, operators, and probabilities. Its creation was one of the central events in the history of modern physics. The older quantum theory had introduced quantized energy, photons, atomic spectra, and the Bohr model, but it lacked a complete mathematical foundation. The transition to modern quantum mechanics began with Louis de Broglie's proposal that matter has wave-like properties and was completed through the nearly simultaneous development of matrix mechanics by Werner Heisenberg, Max Born, and Pascual Jordan, and wave mechanics by Erwin Schrödinger.		'''Timeline: Modern quantum mechanics''' mechanics/Timeline/Modern quantum mechanics is a Book I topic in the Quantum Collection. Key figures in contemporary quantum physics and quantum information (post-1950), including pioneers of quantum computing, entanglement, and modern experiments. Modern quantum mechanics is the form of quantum theory developed from about 1925 onward, when the older, partly phenomenological quantum rules were replaced by a systematic mathematical theory of states, observables, operators, and probabilities. Its creation was one of the central events in the history of modern physics. The older quantum theory had introduced quantized energy, photons, atomic spectra, and the Bohr model, but it lacked a complete mathematical foundation. The transition to modern quantum mechanics began with Louis de Broglie's proposal that matter has wave-like properties and was completed through the nearly simultaneous development of matrix mechanics by Werner Heisenberg, Max Born, and Pascual Jordan, and wave mechanics by Erwin Schrödinger. Modern quantum mechanics is the form of quantum theory developed from about 1925 onward, when the older, partly phenomenological quantum rules were replaced by a systematic mathematical theory of states, observables, operators, and probabilities. Its creation was one of the central events in the history of modern physics. The older quantum theory had introduced quantized energy, photons, atomic spectra, and the Bohr model, but it lacked a complete mathematical foundation. The transition to modern quantum mechanics began with Louis de Broglie's proposal that matter has wave-like properties and was completed through the nearly simultaneous development of matrix mechanics by Werner Heisenberg, Max Born, and Pascual Jordan, and wave mechanics by Erwin Schrödinger. In 1924, de Broglie proposed that particles of matter, such as electrons, possess an associated wavelength.
	~~</div>~~
	~~</div>~~

	~~'''~~Modern quantum mechanics~~'''~~ is the form of quantum theory developed from about 1925 onward, when the older, partly phenomenological quantum rules were replaced by a systematic mathematical theory of states, observables, operators, and probabilities. Its creation was one of the central events in the history of modern physics.

	The older quantum theory had introduced quantized energy, photons, atomic spectra, and the Bohr model, but it lacked a complete mathematical foundation. The transition to modern quantum mechanics began with Louis de Broglie's proposal that matter has wave-like properties and was completed through the nearly simultaneous development of matrix mechanics by Werner Heisenberg, Max Born, and Pascual Jordan, and wave mechanics by Erwin Schrödinger.~~<ref name="Whittaker">{{Cite book \|last=Whittaker \|first=Edmund T. \|title=A history of the theories of aether & electricity. 2: The modern theories~~, 1900–1926 \|date=1989 \|publisher=Dover Publications \|isbn=978-0-486-26126-3 \|edition=Reprint \|location=New York}}</ref><ref name="Hanle">{{citation \|last=Hanle \|first=P. A. \|title=Erwin Schrödinger's Reaction to Louis de Broglie~~'s Thesis on the Quantum Theory \|journal=Isis \|volume=68 \|issue=4 \|pages=606–609 \|date=December 1977 \|doi=10~~.~~1086/351880 \|s2cid=121913205}}</ref>~~
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	{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}		{{Short description\|Quantum Collection topic on Quantum mechanics/Timeline/Modern quantum mechanics}}

	{{Quantum book backlink\|Timeline}}		{{Quantum book backlink\|Timeline}}
	{{Quantum article nav\|previous=Physics:Quantum mechanics/Timeline/Old quantum theory\|previous label=Timeline: Old quantum theory\|next=Physics:Quantum mechanics/Timeline/Quantum field theory era\|next label=Timeline: Quantum field theory era}}		{{Quantum article nav\|previous=Physics:Quantum mechanics/Timeline/Old quantum theory\|previous label=Timeline: Old quantum theory\|next=Physics:Quantum mechanics/Timeline/Quantum field theory era\|next label=Timeline: Quantum field theory era}}

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	'''Modern quantum mechanics''' is the form of quantum theory developed from about 1925 onward, when the older, partly phenomenological quantum rules were replaced by a systematic mathematical theory of states, observables, operators, and probabilities. Its creation was one of the central events in the history of modern physics.		'''Modern quantum mechanics''' is the form of quantum theory developed from about 1925 onward, when the older, partly phenomenological quantum rules were replaced by a systematic mathematical theory of states, observables, operators, and probabilities. Its creation was one of the central events in the history of modern physics.

	The older quantum theory had introduced quantized energy, photons, atomic spectra, and the Bohr model, but it lacked a complete mathematical foundation. The transition to modern quantum mechanics began with Louis de Broglie's proposal that matter has wave-like properties and was completed through the nearly simultaneous development of [[matrix mechanics]] by Werner Heisenberg, Max Born, and Pascual Jordan, and [[wave mechanics]] by Erwin Schrödinger.<ref name="Whittaker">{{Cite book \|last=Whittaker \|first=Edmund T. \|title=A history of the theories of aether & electricity. 2: The modern theories, 1900–1926 \|date=1989 \|publisher=Dover Publications \|isbn=978-0-486-26126-3 \|edition=Reprint \|location=New York}}</ref><ref name="Hanle">{{citation \|last=Hanle \|first=P. A. \|title=Erwin Schrödinger's Reaction to Louis de Broglie's Thesis on the Quantum Theory \|journal=Isis \|volume=68 \|issue=4 \|pages=606–609 \|date=December 1977 \|doi=10.1086/351880 \|s2cid=121913205}}</ref>		The older quantum theory had introduced quantized energy, photons, atomic spectra, and the Bohr model, but it lacked a complete mathematical foundation. The transition to modern quantum mechanics began with Louis de Broglie's proposal that matter has wave-like properties and was completed through the nearly simultaneous development of matrix mechanics by Werner Heisenberg, Max Born, and Pascual Jordan, and wave mechanics by Erwin Schrödinger.<ref name="Whittaker">{{Cite book \|last=Whittaker \|first=Edmund T. \|title=A history of the theories of aether & electricity. 2: The modern theories, 1900–1926 \|date=1989 \|publisher=Dover Publications \|isbn=978-0-486-26126-3 \|edition=Reprint \|location=New York}}</ref><ref name="Hanle">{{citation \|last=Hanle \|first=P. A. \|title=Erwin Schrödinger's Reaction to Louis de Broglie's Thesis on the Quantum Theory \|journal=Isis \|volume=68 \|issue=4 \|pages=606–609 \|date=December 1977 \|doi=10.1086/351880 \|s2cid=121913205}}</ref>
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	'''Wave mechanics''' was developed by Schrödinger in 1926. Building on de Broglie's matter-wave hypothesis, Schrödinger introduced a wave equation whose solutions describe the possible quantum states of a system.		'''Wave mechanics''' was developed by Schrödinger in 1926. Building on de Broglie's matter-wave hypothesis, Schrödinger introduced a wave equation whose solutions describe the possible quantum states of a system.

	The central object in wave mechanics is the [[wave function]], usually denoted by <math>\psi</math>. The wave function does not describe a classical material wave. Instead, through Max Born's interpretation, it provides probability amplitudes: the square of its magnitude gives probabilities for measurement outcomes.		The central object in wave mechanics is the wave function, usually denoted by <math>\psi</math>. The wave function does not describe a classical material wave. Instead, through Max Born's interpretation, it provides probability amplitudes: the square of its magnitude gives probabilities for measurement outcomes.

	Schrödinger's equation successfully reproduced the hydrogen spectrum and gave a deeper explanation of atomic orbitals. In this picture, electrons do not move in definite planetary orbits around the nucleus; instead, they occupy quantum states represented by probability distributions.		Schrödinger's equation successfully reproduced the hydrogen spectrum and gave a deeper explanation of atomic orbitals. In this picture, electrons do not move in definite planetary orbits around the nucleus; instead, they occupy quantum states represented by probability distributions.
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	[[File:Paul Dirac, 1933.jpg\|thumb\|250px\|right\|Paul Dirac helped unify quantum mechanics with special relativity and introduced powerful formal methods.]]		[[File:Paul Dirac, 1933.jpg\|thumb\|250px\|right\|Paul Dirac helped unify quantum mechanics with special relativity and introduced powerful formal methods.]]

	Paul Dirac played a major role in the formal development of quantum mechanics. Around 1927, he began to connect quantum theory with [[special relativity]], eventually producing the Dirac equation for the electron. The equation predicted electron spin and led to the prediction of the [[positron]].		Paul Dirac played a major role in the formal development of quantum mechanics. Around 1927, he began to connect quantum theory with special relativity, eventually producing the Dirac equation for the electron. The equation predicted electron spin and led to the prediction of the positron.

	Dirac also introduced influential mathematical notation and operator methods, including [[bra–ket notation]], which became standard in quantum theory. His 1930 textbook helped establish the abstract formulation of quantum mechanics used in modern physics.		Dirac also introduced influential mathematical notation and operator methods, including bra–ket notation, which became standard in quantum theory. His 1930 textbook helped establish the abstract formulation of quantum mechanics used in modern physics.

	During the same period, John von Neumann developed a rigorous mathematical foundation for quantum mechanics using linear operators on Hilbert spaces. This abstract framework remains central to the modern formulation of the theory.		During the same period, John von Neumann developed a rigorous mathematical foundation for quantum mechanics using linear operators on Hilbert spaces. This abstract framework remains central to the modern formulation of the theory.
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	== Toward quantum field theory ==		== Toward quantum field theory ==

	Modern quantum mechanics was first developed for particles and atoms, but physicists soon attempted to apply quantum principles to fields. Beginning in the late 1920s, work by Dirac, Jordan, Pauli, and others led to early forms of [[quantum field theory]].		Modern quantum mechanics was first developed for particles and atoms, but physicists soon attempted to apply quantum principles to fields. Beginning in the late 1920s, work by Dirac, Jordan, Pauli, and others led to early forms of quantum field theory.

	The most successful early quantum field theory was [[quantum electrodynamics]], which describes the interaction of charged particles with the electromagnetic field. It was later reformulated and refined by Richard Feynman, Julian Schwinger, Shin'ichirō Tomonaga, and Freeman Dyson. Quantum field theory eventually became the language of particle physics and the foundation of the Standard Model.		The most successful early quantum field theory was quantum electrodynamics, which describes the interaction of charged particles with the electromagnetic field. It was later reformulated and refined by Richard Feynman, Julian Schwinger, Shin'ichirō Tomonaga, and Freeman Dyson. Quantum field theory eventually became the language of particle physics and the foundation of the Standard Model.

	[[File:Quantum_book1_mechanics_timeline_modern_quantum_mechanics_yellow.png\|thumb\|300px\|right\|A Feynman diagram. Diagrammatic methods became central in later quantum field theory.]]		[[File:Quantum_book1_mechanics_timeline_modern_quantum_mechanics_yellow.png\|thumb\|300px\|right\|A Feynman diagram. Diagrammatic methods became central in later quantum field theory.]]