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Thetimeline of quantum mechanics is a list of key events in thehistory of quantum mechanics,quantum field theories andquantum chemistry.

• 1801 –Thomas Young establishes that light made up of waves with hisDouble-slit experiment.
• 1859 –Gustav Kirchhoff introduces the concept of ablackbody and proves that its emission spectrum depends only on its temperature.^[1]
• 1860–1900 –Ludwig Eduard Boltzmann,James Clerk Maxwell and others develop the theory ofstatistical mechanics. Boltzmann argues thatentropy is a measure of disorder.^[1]
• 1877 – Boltzmann suggests that the energy levels of a physical system could be discrete based on statistical mechanics and mathematical arguments; also produces the first circle diagram representation, or atomic model of a molecule (such as an iodine gas molecule) in terms of the overlapping terms α and β, later (in 1928) called molecular orbitals, of the constituting atoms.
• 1885 –Johann Jakob Balmer discovers a numerical relationship between visible spectral lines ofhydrogen, theBalmer series.
• 1887 –Heinrich Hertz discovers the photoelectric effect, shown by Einstein in 1905 to involvequanta of light.
• 1888 – Hertz demonstrates experimentally that electromagnetic waves exist, as predicted by Maxwell.^[1]
• 1888 –Johannes Rydberg modifies the Balmer formula to include all spectral series of lines for the hydrogen atom, producing the Rydberg formula that is employed later byNiels Bohr and others to verify Bohr's first quantum model of the atom.
• 1895 –Wilhelm Conrad Röntgen discovers X-rays in experiments with electron beams in plasma.^[1]
• 1896 –Antoine Henri Becquerel accidentally discoversradioactivity while investigating the work ofWilhelm Conrad Röntgen; he finds that uranium salts emit radiation that resembled Röntgen's X-rays in their penetrating power. In one experiment, Becquerel wraps a sample of a phosphorescent substance, potassium uranyl sulfate, in photographic plates surrounded by very thick black paper in preparation for an experiment with bright sunlight; then, to his surprise, the photographic plates are already exposed before the experiment starts, showing a projected image of his sample.^[1][2]
• 1896–1897 –Pieter Zeeman first observes theZeeman splitting effect by applying a magnetic field to light sources.^[3]
• 1896–1897 –Marie Curie (née Skłodowska, Becquerel's doctoral student) investigates uranium salt samples using a very sensitiveelectrometer device that was invented 15 years before by her husband and his brother Jacques Curie to measure electrical charge. She discovers that rays emitted by the uranium salt samples make the surrounding air electrically conductive, and measures the emitted rays' intensity. In April 1898, through a systematic search of substances, she finds thatthorium compounds, like those of uranium, emitted "Becquerel rays", thus preceding the work ofFrederick Soddy andErnest Rutherford on the nuclear decay of thorium toradium by three years.^[4]
• 1897:
  • Ivan Borgman demonstrates thatX-rays andradioactive materials inducethermoluminescence.
  • J. J. Thomson's experimentation withcathode rays led him to suggest a fundamental unit more than a 1,000 times smaller than an atom, based on the highcharge-to-mass ratio. He called the particle a "corpuscle", but later scientists preferred the termelectron.
  • Joseph Larmor explained the splitting of thespectral lines in amagnetic field by theoscillation of electrons.^[5][6]
  • Larmor, created the first solar system model of the atom in 1897. He also postulated the proton, calling it a "positive electron". He said the destruction of this type of atom making up matter "is an occurrence of infinitely small probability".^[7]
• 1899–1903 –Ernest Rutherford investigates radioactivity. He coins the termsalpha andbeta rays in 1899 to describe the two distinct types of radiation emitted bythorium anduranium salts. Rutherford is joined at McGill University in 1900 byFrederick Soddy and together they discovernuclear transmutation when they find in 1902 that radioactive thorium is converting itself intoradium through a process ofnuclear decay and a gas (later found to be⁴
  ₂He); they report their interpretation of radioactivity in 1903.^[8] Rutherford becomes known as the "father ofnuclear physics" with hisnuclear atom model of 1911.^[9]

• 1900 – To explainblack-body radiation (1862),Max Planck suggests that electromagnetic energy could only be emitted in quantized form, i.e. the energy could only be a multiple of an elementary unitE =hν, whereh is thePlanck constant andν is the frequency of the radiation.
• 1902 – To explain theoctet rule (1893),Gilbert N. Lewis develops the "cubical atom" theory in which electrons in the form of dots are positioned at the corner of a cube. Predicts that single, double, or triple "bonds" result when two atoms are held together by multiple pairs of electrons (one pair for each bond) located between the two atoms.
• 1903 – Antoine Becquerel, Pierre Curie and Marie Curie share the 1903 Nobel Prize in Physics for their work onspontaneous radioactivity.
• 1904 –Richard Abegg notes the pattern that the numerical difference between the maximum positive valence, such as +6 for H₂SO₄, and the maximum negative valence, such as −2 for H₂S, of an element tends to be eight (Abegg's rule).
• 1905 :
  • Albert Einstein explains thephotoelectric effect (reported in 1887 byHeinrich Hertz), i.e. that shining light on certain materials can function to eject electrons from the material. He postulates, as based on Planck's quantum hypothesis (1900), that light itself consists of individual quantum particles (photons).
  • Einstein explains the effects ofBrownian motion as caused by thekinetic energy (i.e., movement) of atoms, which was subsequently, experimentally verified byJean Baptiste Perrin, thereby settling the century-long dispute about the validity ofJohn Dalton'satomic theory.
  • Einstein publishes hisspecial theory of relativity
  • Einstein theoretically derives theequivalence of matter and energy.
• 1907 to 1917 – Ernest Rutherford: To test hisplanetary model of 1904, later known as theRutherford model, he sent a beam of positively chargedalpha particles onto a gold foil and noticed that some bounced back, thus showing that an atom has a small-sized positively chargedatomic nucleus at its center. However, he received in 1908 the Nobel Prize in Chemistry "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances",^[10] which followed on the work of Marie Curie, not for his planetary model of the atom; he is also widely credited with first "splitting the atom" in 1917. In 1911 Ernest Rutherford explained theGeiger–Marsden experiment by invoking anuclear atom model and derived theRutherford cross section.
• 1909 –Geoffrey Ingram Taylor demonstrates that interference patterns of light were generated even when the light energy introduced consisted of only one photon. This discovery of thewave–particle duality of matter and energy is fundamental to the later development ofquantum field theory.
• 1909 and 1916 – Einstein shows that, ifPlanck's law of black-body radiation is accepted, the energy quanta must also carrymomentump =h /λ, making them full-fledgedparticles.

• 1911:
  • Lise Meitner andOtto Hahn perform an experiment that shows that the energies ofelectrons emitted bybeta decay had a continuous rather than discrete spectrum. This is in apparent contradiction to the law of conservation of energy, as it appeared that energy was lost in the beta decay process. A second problem is that the spin of thenitrogen-14 atom was 1, in contradiction to the Rutherford prediction of1⁄2. These anomalies are later explained by the discoveries of theneutrino and theneutron.
  • Ștefan Procopiu performs experiments in which he determines the correct value of electron's magnetic dipole moment,μ_B =9.27×10⁻²¹ erg·Oe⁻¹ (in 1913 he is also able to calculate a theoretical value of theBohr magneton based on Planck's quantum theory).
  • John William Nicholson is noted as the first to create an atomic model that quantized angular momentum ash/2π.^[11][12]Niels Bohr quoted him in his 1913 paper of theBohr model of the atom.^[13]
• 1912 –Victor Hess discovers the existence ofcosmic radiation.
• 1912 –Henri Poincaré publishes an influential mathematical argument in support of the essential nature of energy quanta.^[14][15]
• 1913:
  • Robert Andrews Millikan publishes the results of his "oil drop" experiment, in which he precisely determines theelectric charge of the electron. Determination of the fundamental unit of electric charge makes it possible to calculate theAvogadro constant (which is the number of atoms or molecules in onemole of any substance) and thereby to determine theatomic weight of the atoms of eachelement.
  • Niels Bohr publishes his 1913 paper of theBohr model of the atom.^[16]
  • Ștefan Procopiu publishes a theoretical paper with the correct value of the electron's magnetic dipole momentμ_B.^[17]
  • Niels Bohr obtains theoretically the value of the electron's magnetic dipole momentμ_B as a consequence of his atom model
  • Johannes Stark andAntonino Lo Surdo independently discover the shifting and splitting of the spectral lines of atoms and molecules due to the presence of the light source in an external static electric field.
  • To explain theRydberg formula (1888), which correctly modeled the light emission spectra of atomic hydrogen, Bohr hypothesizes that negatively charged electrons revolve around a positively charged nucleus at certain fixed "quantum" distances and that each of these "spherical orbits" has a specific energy associated with it such that electron movements between orbits requires "quantum" emissions or absorptions of energy.
• 1914 –James Franck andGustav Hertz report theirexperiment on electron collisions with mercury atoms, which provides a new test of Bohr's quantized model of atomic energy levels.^[18]
• 1915 – Einstein first presents to thePrussian Academy of Science what are now known as theEinstein field equations. These equations specify how the geometry of space and time is influenced by whatever matter is present, and form the core of Einstein'sGeneral Theory of Relativity. Although this theory is not directly applicable to quantum mechanics, theorists ofquantum gravity seek to reconcile them.
• 1916 –Paul Epstein^[19] andKarl Schwarzschild,^[20] working independently, derive equations for the linear and quadraticStark effect in hydrogen.
• 1916 –Gilbert N. Lewis conceives the theoretical basis ofLewis dot formulas, diagrams that show thebonding betweenatoms of amolecule and thelone pairs of electrons that may exist in the molecule.^[21]
• 1916 – To account for theZeeman effect (1896), i.e. that atomic absorption or emission spectral lines change when the light source is subjected to a magnetic field,Arnold Sommerfeld suggests there might be "elliptical orbits" in atoms in addition to spherical orbits.
• 1918 – Sir Ernest Rutherford notices that, whenalpha particles are shot intonitrogen gas, hisscintillation detectors shows the signatures of hydrogen nuclei. Rutherford determines that the only place this hydrogen could have come from was the nitrogen, and therefore nitrogen must contain hydrogen nuclei. He thus suggests that the hydrogen nucleus, which is known to have anatomic number of 1, is anelementary particle, which he decides must be theprotons hypothesized byEugen Goldstein.
• 1919 – Building on the work of Lewis (1916),Irving Langmuir coins the term "covalence" and postulates thatcoordinate covalent bonds occur when two electrons of a pair of atoms come from both atoms and are equally shared by them, thus explaining the fundamental nature of chemical bonding and molecular chemistry.

• 1920 –Hendrik Kramers usesBohr–Sommerfeld quantization to derive formulas for intensities of spectral transitions of theStark effect. Kramers also includes the effect offine structure, including corrections for relativistic kinetic energy and coupling between electron spin and orbit.^[22]
• 1921–1922 – Frederick Soddy receives the Nobel Prize for 1921 in Chemistry one year later, in 1922, "for his contributions to our knowledge of the chemistry of radioactive substances, and his investigations into the origin and nature ofisotopes"; he writes in his Nobel Lecture of 1922: "The interpretation of radioactivity which was published in 1903 by Sir Ernest Rutherford and myself ascribed the phenomena to thespontaneous disintegration of the atoms of the radio-element, whereby a part of the original atom was violently ejected as a radiant particle, and the remainder formed a totally new kind of atom with a distinct chemical and physical character."
• 1922:
  • Arthur Compton finds that X-ray wavelengths increase due to scattering of theradiant energy byfree electrons. The scatteredquanta have less energy than the quanta of the original ray. This discovery, known as theCompton effect orCompton scattering, demonstrates theparticle concept ofelectromagnetic radiation.
  • Otto Stern andWalther Gerlach perform theStern–Gerlach experiment, which detects discrete values of angular momentum for atoms in the ground state passing through an inhomogeneous magnetic field leading to the discovery of thespin of the electron.
  • Bohr updates his model of the atom to better explain the properties of the periodic table by assuming that certain numbers of electrons (for example 2, 8 and 18) corresponded to stable "closed shells", presaging orbital theory.
• 1923:
  • Pierre Auger discovers theAuger effect, where filling the inner-shell vacancy of an atom is accompanied by the emission of an electron from the same atom.
  • Louis de Broglie extendswave–particle duality to particles, postulating that electrons in motion are associated with waves. He predicts that the wavelengths are given by thePlanck constanth divided by themomentum of themv =p of theelectron:λ =h /mv =h /p.^[1]
  • Gilbert N. Lewis creates the theory ofLewis acids and bases based on the properties of electrons in molecules, defining anacid as accepting an electron lone pair from abase.
• 1924 –Satyendra Nath Bose explains Planck's law using a new statistical law that governsbosons, and Einstein generalizes it to predictBose–Einstein condensate. The theory becomes known asBose–Einstein statistics.^[1]
• 1924 –Wolfgang Pauli outlines the "Pauli exclusion principle", which states that no two identicalfermions may occupy the same quantum state simultaneously, a fact that explains many features of theperiodic table.^[1]
• 1925:
  • George Uhlenbeck andSamuel Goudsmit postulate the existence ofelectron spin.^[1]
  • Friedrich Hund outlinesHund's rule of Maximum Multiplicity, which states that when electrons are added successively to an atom as many levels or orbits are singly occupied as possible before any pairing of electrons with opposite spin occurs and made the distinction that the inner electrons in molecules remained inatomic orbitals and only thevalence electrons needed to be inmolecular orbitals involving both nuclei.
  • Werner Heisenberg published hisUmdeutung paper, reinterpreting quantum mechanics using non-commutative algebra.
  • Heisenberg,Max Born, andPascual Jordan develop thematrix mechanics formulation of quantum Mechanics.^[1]
• 1926:
  • Lewis coins the termphoton in a letter to the scientific journalNature, which he derives from the Greek word for light, φως (transliterated phôs).^[23]
  • Oskar Klein andWalter Gordon state their relativistic quantum wave equation, later called theKlein–Gordon equation.
  • Enrico Fermi discovers thespin–statistics theorem connection.
  • Paul Dirac introducesFermi–Dirac statistics.
  • Erwin Schrödinger uses De Broglie's electron wave postulate (1924) to develop a "wave equation" that represents mathematically the distribution of a charge of an electron distributed through space, being spherically symmetric or prominent in certain directions, i.e. directedvalence bonds, which gives the correct values for spectral lines of the hydrogen atom; also introduces theHamiltonian operator in quantum mechanics.
  • Max Born postulates the statistical interpretation of the quantum mechanical wave function (Born rule)
  • Paul Epstein reconsiders the linear and quadratic Stark effect from the point of view of the new quantum theory, using the equations of Schrödinger and others. The derived equations for the line intensities are a decided improvement over previous results obtained byHans Kramers.^[24]
• 1926 to 1932 –John von Neumann published theMathematical Foundations of Quantum Mechanics in terms of Hermitian operators onHilbert spaces, subsequently published in 1932 as a basic textbook on themathematical formulation of quantum mechanics.^[1][25][26]
• 1927:
  • Werner Heisenberg formulates the quantumuncertainty principle.^[1]
  • Niels Bohr and Werner Heisenberg develop theCopenhagen interpretation of the probabilistic nature of wavefunctions.
  • Born andJ. Robert Oppenheimer introduce theBorn–Oppenheimer approximation, which allows the quick approximation of the energy and wavefunctions of smaller molecules.
  • Walter Heitler andFritz London introduce the concepts ofvalence bond theory and apply it to the hydrogen molecule.
  • Llewellyn Thomas andFermi develop theThomas–Fermi model for agas in a box.
  • Chandrasekhara Venkata Raman studies optical photon scattering by electrons.
  • Dirac states his relativistic electron quantum wave equation, theDirac equation.
  • Charles Galton Darwin andWalter Gordon solve theDirac equation for a Coulomb potential.
  • Charles Drummond Ellis (along withJames Chadwick and colleagues) finally establish clearly that the beta decay spectrum is in fact continuous and not discrete, posing a problem that will later be solved by theorizing (and later discovering) the existence of theneutrino.
  • Walter Heitler uses Schrödinger's wave equation to show how two hydrogen atomwavefunctions join, with plus, minus, and exchange terms, to form acovalent bond.
  • Robert Mulliken works, in coordination with Hund, to develop a molecular orbital theory where electrons are assigned to states that extend over an entire molecule and, in 1932, introduces many new molecular orbital terminologies, such asσ bond,π bond, andδ bond.
  • Eugene Wigner relatesdegeneracies of quantum states toirreducible representations of symmetry groups.
  • Hermann Klaus Hugo Weyl proves in collaboration with his studentFritz Peter a fundamental theorem in harmonic analysis—thePeter–Weyl theorem—relevant togroup representations in quantum theory (including thecomplete reducibility ofunitary representations of acompacttopological group);^[27] introduces theWeyl quantization, and earlier, in 1918, introduces the concept of gauge and agauge theory; later in 1935 he introduces and characterizes with Richard Bauer the concept ofspinor inn dimensions.^[28]
• 1928:
  • Linus Pauling outlines the nature of thechemical bond: uses Heitler's quantum mechanical covalent bond model to outline thequantum mechanical basis for all types of molecular structure and bonding and suggests that different types of bonds in molecules can become equalized by rapid shifting of electrons, a process called "resonance" (1931), such that resonance hybrids contain contributions from the different possible electronic configurations.
  • Friedrich Hund andRobert S. Mulliken introduce the concept ofmolecular orbitals.
  • Born andVladimir Fock formulate and prove theadiabatic theorem, which states that a physical system shall remain in its instantaneouseigenstate if a givenperturbation is acting on it slowly enough and if there is a gap between theeigenvalue and the rest of theHamiltonian'sspectrum.
• 1929:
  • Oskar Klein discovers theKlein paradox
  • Oskar Klein andYoshio Nishina derive the Klein–Nishina cross section for high energy photon scattering by electrons.
  • SirNevill Mott derives theMott cross section for the Coulomb scattering of relativistic electrons.
  • John Lennard-Jones introduces thelinear combination of atomic orbitals approximation for the calculation of molecular orbitals.
  • Fritz Houtermans andRobert d'Escourt Atkinson propose that stars release energy by nuclear fusion.^[1]

• 1930
  • Dirac hypothesizes the existence of the positron.^[1]
  • Dirac's textbookThe Principles of Quantum Mechanics is published, becoming a standard reference book that is still used today.
  • Erich Hückel introduces theHückel molecular orbital method, which expands on orbital theory to determine the energies of orbitals ofpi electrons in conjugated hydrocarbon systems.
  • Fritz London explainsvan der Waals forces as due to the interacting fluctuatingdipole moments between molecules
  • Pauli suggests in a famous letter that, in addition to electrons and protons, atoms also contain an extremely light neutral particle that he calls the "neutron". He suggests that this "neutron" is also emitted during beta decay and has simply not yet been observed. Later it is determined that this particle is actually the almost massless neutrino.^[1]
• 1931:
  • John Lennard-Jones proposes theLennard-Jones inter-atomic potential.
  • Walther Bothe andHerbert Becker find that if the very energeticalpha particles emitted frompolonium fall on certain light elements, specificallyberyllium,boron, orlithium, an unusually penetrating radiation is produced. At first this radiation is thought to begamma radiation, although it is more penetrating than any gamma rays known, and the details of experimental results are very difficult to interpret on this basis. Some scientists begin to hypothesize the possible existence of another fundamental particle.
  • Erich Hückel redefines the property ofaromaticity in a quantum mechanical context by introducing the4n+2 rule, orHückel's rule, which predicts whether an organicplanar ringmolecule will have aromatic properties.
  • Ernst Ruska creates the firstelectron microscope.^[1]
  • Ernest Lawrence creates the firstcyclotron and founds the Radiation Laboratory, later theLawrence Berkeley National Laboratory; in 1939 he was awarded the Nobel Prize in Physics for his work on the cyclotron.
• 1932:
  • Irène Joliot-Curie andFrédéric Joliot show that if the unknown radiation generated by alpha particles falls on paraffin or any other hydrogen-containing compound, it ejectsprotons of very high energy. This is not in itself inconsistent with the proposedgamma ray nature of the new radiation, but detailed quantitative analysis of the data become increasingly difficult to reconcile with such a hypothesis.
  • James Chadwick performs a series of experiments showing that the gamma ray hypothesis for the unknown radiation produced by alpha particles is untenable, and that the new particles must be theneutrons hypothesized by Fermi.^[1]
  • Werner Heisenberg appliesperturbation theory to the two-electron problem to show howresonance arising from electron exchange can explainForce carriers.
  • Mark Oliphant: Building upon the nuclear transmutation experiments of Ernest Rutherford done a few years earlier, observes fusion of light nuclei (hydrogen isotopes). The steps of the main cycle of nuclear fusion in stars are subsequently worked out by Hans Bethe over the next decade.
  • Carl D. Anderson experimentally proves the existence of the positron.^[1]
• 1933 – Following Chadwick's experiments, Fermi renames Pauli's "neutron" to neutrino to distinguish it from Chadwick's theory of the much more massive neutron.
• 1933 –Leó Szilárd first theorizes the concept of a nuclear chain reaction. He files a patent for his idea of a simple nuclear reactor the following year.
• 1934:
  • Fermi publishes a very successfulmodel of beta decay in which neutrinos are produced.
  • Fermi studies the effects of bombardinguranium isotopes with neutrons.
  • N. N. Semyonov develops the total quantitative chain chemical reaction theory, later the basis of various high technologies using the incineration of gas mixtures. The idea is also used for the description of the nuclear reaction.
  • Irène Joliot-Curie and Frédéric Joliot-Curie discoverartificial radioactivity and are jointly awarded the 1935 Nobel Prize in Chemistry^[29]
• 1935:
  • Einstein,Boris Podolsky, andNathan Rosen describe theEPR paradox, which challenges the completeness of quantum mechanics as it was theorized up to that time. Assuming thatlocal realism is valid, they demonstrated that there would need to behidden parameters to explain how measuring the quantum state of one particle could influence the quantum state of another particle without apparent contact between them.^[30]
  • Schrödinger develops theSchrödinger's cat thought experiment. It illustrates what he saw as the problems of theCopenhagen interpretation of quantum mechanics if subatomic particles can be in two contradictory quantum states at once.
  • Hideki Yukawa predicts the existence of thepion, stating that such a potential arises from the exchange of a massivescalar field, as it would be found in the field of the pion. Prior to Yukawa's paper, it was believed that the scalar fields of thefundamental forces necessitated massless particles.
• 1936 –Alexandru Proca publishes prior toHideki Yukawa his relativistic quantum field equations for a massivevector meson ofspin-1 as a basis fornuclear forces.
• 1936 –Garrett Birkhoff andJohn von Neumann introduceQuantum Logic^[31] in an attempt to reconcile the apparent inconsistency of classical, Boolean logic with the HeisenbergUncertainty Principle of quantum mechanics as applied, for example, to the measurement of complementary (noncommuting)observables in quantum mechanics, such asposition and momentum;^[32] current approaches to quantum logic involvenoncommutative andnon-associativemany-valued logic.^[33][34]
• 1936 –Carl D. Anderson discoversmuons while he is studying cosmic radiation.
• 1937 –Hermann Arthur Jahn andEdward Teller prove, usinggroup theory, that non-linear degenerate molecules are unstable.^[35] The Jahn–Teller theorem essentially states that any non-linear molecule with adegenerate electronic ground state will undergo a geometrical distortion that removes that degeneracy, because the distortion lowers the overall energy of the complex. The latter process is called theJahn–Teller effect; this effect was recently considered also in relation to the superconductivity mechanism inYBCO and otherhigh temperature superconductors. The details of the Jahn–Teller effect are presented with several examples and EPR data in the basic textbook by Abragam and Bleaney (1970).
• 1938 –Charles Coulson makes the first accurate calculation of a molecular orbitalwavefunction with thehydrogen molecule.
• 1938 –Otto Hahn and his assistantFritz Strassmann send a manuscript to Naturwissenschaften reporting they have detected the element barium after bombarding uranium with neutrons. Hahn calls this new phenomenon a 'bursting' of the uranium nucleus. Simultaneously, Hahn communicates these results toLise Meitner. Meitner, and her nephewOtto Robert Frisch, correctly interpret these results as being anuclear fission. Frisch confirms this experimentally on 13 January 1939.
• 1939 –Leó Szilárd and Fermi discover neutron multiplication in uranium, proving that a chain reaction is indeed possible.

• 1942 – A team led by Enrico Fermi creates the first artificial self-sustaining nuclear chain reaction, called Chicago Pile-1, in a racquets court below the bleachers of Stagg Field at the University of Chicago on December 2, 1942.
• 1942 to 1946 –J. Robert Oppenheimer successfully leads theManhattan Project, predictsquantum tunneling and proposes theOppenheimer–Phillips process innuclear fusion
• 1945 – theManhattan Project produces the first nuclear fission explosion on July 16, 1945, in theTrinity test in New Mexico.
• 1945 –John Archibald Wheeler andRichard Feynman originateWheeler–Feynman absorber theory, an interpretation of electrodynamics that supposes that elementary particles are not self-interacting.
• 1946 –Theodor V. Ionescu and Vasile Mihu report the construction of the firsthydrogen maser bystimulated emission of radiation in molecular hydrogen.
• 1947 –Willis Lamb andRobert Retherford measure a small difference inenergy between theenergy levels²S_1/2 and²P_1/2 of thehydrogen atom, known as theLamb shift.
• 1947 –George Rochester andClifford Charles Butler publish twocloud chamber photographs of cosmic ray-induced events, one showing what appears to be a neutral particle decaying into two charged pions, and one that appears to be a charged particle decaying into a charged pion and something neutral. The estimated mass of the new particles is very rough, about half a proton's mass. More examples of these "V-particles" were slow in coming, and they are soon given the namekaons.
• 1948 –Sin-Itiro Tomonaga andJulian Schwinger independently introduceperturbative renormalization as a method of correcting the originalLagrangian of a quantum field theory so as to eliminate a series of infinite terms that would otherwise result.
• 1948 –Richard Feynman states thepath integral formulation of quantum mechanics.
• 1949 –Freeman Dyson determines the equivalence of two formulations ofquantum electrodynamics: Feynman's diagrammaticpath integral formulation and the operator method developed byJulian Schwinger and Tomonaga. A by-product of that demonstration is the invention of theDyson series.^[36]

• 1951:
  • Clemens C. J. Roothaan andGeorge G. Hall derive theRoothaan–Hall equations, putting rigorous molecular orbital methods on a firm basis.
  • Edward Teller, physicist and "father of the hydrogen bomb", andStanislaw Ulam, mathematician, are reported to have written jointly in March 1951 a classified report on "Hydrodynamic Lenses and Radiation Mirrors" that results in the next step in the Manhattan Project.^[37]
  • 1951 and 1952 – at the Manhattan Project, the first planned fusionthermonuclear reaction experiment is carried out successfully in the Spring of 1951 at Eniwetok, based on the work of Edward Teller and Dr.Hans A. Bethe.^[38] TheLos Alamos Laboratory proposes a date in November 1952 for ahydrogen bomb, full-scale test that is apparently carried out.
  • Felix Bloch andEdward Mills Purcell receive a shared Nobel Prize in Physics for their first observations of the quantum phenomenon ofnuclear magnetic resonance previously reported in 1949.^[39][40][41] Purcell reports his contribution asResearch in Nuclear Magnetism, and gives credit to his coworkers such asHerbert S. Gutowsky for their NMR contributions,^[42][43] as well as theoretical researchers ofnuclear magnetism such asJohn Hasbrouck Van Vleck.
• 1952 –Albert W. Overhauser formulates a theory ofdynamic nuclear polarization, also known as theOverhauser Effect; other contenders are the subsequent theory of Ionel Solomon reported in 1955 that includes theSolomon equations for the dynamics of coupled spins, and that of R. Kaiser in 1963. The general Overhauser effect is first demonstrated experimentally by T. R. Carver andCharles P. Slichter in 1953.^[44]
• 1952 –Donald A. Glaser creates thebubble chamber, which allows detection of electrically charged particles by surrounding them by a bubble. Properties of the particles such as momentum can be determined by studying their helical paths. Glaser receives a Nobel prize in 1960 for his invention.
• 1953 –Charles H. Townes, collaborating withJames P. Gordon, andHerbert J. Zeiger, builds the first ammoniamaser; receives a Nobel prize in 1964 for his experimental success in producingcoherent radiation by atoms and molecules.
• 1954 –Chen Ning Yang andRobert Mills derive agauge theory fornonabelian groups, leading to the successful formulation of bothelectroweak unification andquantum chromodynamics.
• 1955 – Ionel Solomon develops the firstnuclear magnetic resonance theory ofmagnetic dipole couplednuclear spins and of theNuclear Overhauser effect.
• 1956 – P. Kuroda predicts that self-sustaining nuclear chain reactions should occur in natural uranium deposits.
• 1956 –Chien-Shiung Wu carries out theWu Experiment, which observes parity violation incobalt-60 decay, showing that parity violation is present in theweak interaction.
• 1956 –Clyde L. Cowan andFrederick Reines experimentally prove the existence of the neutrino.
• 1957 –John Bardeen,Leon Cooper andJohn Robert Schrieffer propose their quantumBCS theory of low temperaturesuperconductivity, for which they receive a Nobel prize in 1972. The theory represents superconductivity as a macroscopic quantum coherence phenomenon involvingphonon coupled electron pairs with opposite spin
• 1957 –William Alfred Fowler,Margaret Burbidge,Geoffrey Burbidge, andFred Hoyle, in their 1957 paperSynthesis of the Elements in Stars, show that the abundances of essentially all but the lightest chemical elements can be explained by the process ofnucleosynthesis in stars.
• 1957 –Hugh Everett formulates themany-worlds interpretation of quantum mechanics, which states that every possible quantum outcome is realized in divergent, non-communicating parallel universes inquantum superposition.^[45][46]
• 1958–1959 –magic angle spinning described by Edward Raymond Andrew, A. Bradbury, and R. G. Eades, and independently in 1959 by I. J. Lowe.^[47]

• 1961 –Claus Jönsson performsYoung'sdouble-slit experiment (1909) for the first time with particles other than photons by using electrons and with similar results, confirming that massive particles also behaved according to the wave–particle duality that is a fundamental principle of quantum field theory.
• 1961 –Anatole Abragam publishes the fundamental textbook on the quantum theory ofNuclear Magnetic Resonance entitledThe Principles of Nuclear Magnetism;^[49]
• 1961 –Sheldon Glashow extends theelectroweak interaction models developed by Julian Schwinger by including a short rangeneutral current, the Z_o. The resulting symmetry structure that Glashow proposes, SU(2) × U(1), forms the basis of the accepted theory of the electroweak interactions.
• 1962 –Leon M. Lederman,Melvin Schwartz andJack Steinberger show that more than one type of neutrino exists by detecting interactions of themuon neutrino (already hypothesised with the name "neutretto")
• 1962 –Jeffrey Goldstone,Yoichiro Nambu,Abdus Salam, andSteven Weinberg develop what is now known asGoldstone's Theorem: if there is a continuous symmetry transformation under which the Lagrangian is invariant, then either the vacuum state is also invariant under the transformation, or there must be spinless particles of zero mass, thereafter calledNambu–Goldstone bosons.
• 1962 to 1973 –Brian David Josephson, predicts correctly the quantum tunneling effect involving superconducting currents while he is a PhD student under the supervision of Professor Brian Pippard at the Royal Society Mond Laboratory in Cambridge, UK; subsequently, in 1964, he applies his theory to coupled superconductors. The effect is later demonstrated experimentally at Bell Labs in the USA. For his important quantum discovery he is awarded the Nobel Prize in Physics in 1973.^[50]
• 1963 –Eugene P. Wigner lays the foundation for the theory of symmetries in quantum mechanics as well as for basic research into the structure of the atomic nucleus; makes important "contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles"; he shares half of his Nobel prize in Physics withMaria Goeppert-Mayer andJ. Hans D. Jensen.
• 1963 –Maria Goeppert Mayer andJ. Hans D. Jensen share withEugene P. Wigner half of the Nobel Prize in Physics in 1963 "for their discoveries concerningnuclear shell structure theory".^[51]
• 1964 –John Stewart Bell puts forthBell's theorem, which used testableinequality relations to show the flaws in the earlierEinstein–Podolsky–Rosen paradox and prove that no physical theory oflocal hidden variables can ever reproduce all of the predictions of quantum mechanics. This inaugurated the study ofquantum entanglement, the phenomenon in which separate particles share the same quantum state despite being at a distance from each other.
• 1964 –Nikolai G. Basov andAleksandr M. Prokhorov share the Nobel Prize in Physics in 1964 for, respectively,semiconductor lasers andQuantum Electronics; they also share the prize withCharles Hard Townes, the inventor of the ammoniummaser.
• 1969 to 1977 – SirNevill Mott andPhilip Warren Anderson publish quantum theories for electrons in non-crystalline solids, such as glasses and amorphous semiconductors; receive in 1977 a Nobel prize in Physics for their investigations into the electronic structure of magnetic and disordered systems, which allow for the development of electronic switching and memory devices in computers. The prize is shared withJohn Hasbrouck Van Vleck for his contributions to the understanding of the behavior of electrons in magnetic solids; he established the fundamentals of the quantum mechanical theory of magnetism and the crystal field theory (chemical bonding in metal complexes) and is regarded as the Father of modern Magnetism.
• 1969 and 1970 –Theodor V. Ionescu, Radu Pârvan and I.C. Baianu observe and report quantum amplified stimulation of electromagnetic radiation in hot deuterium plasmas in a longitudinal magnetic field; publish a quantum theory of the amplified coherent emission of radiowaves and microwaves by focused electron beams coupled to ions in hot plasmas.

• 1971 –Martinus J. G. Veltman andGerardus 't Hooft show that, if the symmetries ofYang–Mills theory are broken according to the method suggested byPeter Higgs, then Yang–Mills theory can be renormalized. The renormalization of Yang–Mills Theory predicts the existence of a massless particle, called thegluon, which could explain the nuclearstrong force. It also explains how the particles of theweak interaction, theW and Z bosons, obtain their mass viaspontaneous symmetry breaking and theYukawa interaction.
• 1972 –Francis Perrin discovers "natural nuclear fission reactors" in uranium deposits inOklo,Gabon, where analysis of isotope ratios demonstrate that self-sustaining, nuclear chain reactions have occurred. The conditions under which a natural nuclear reactor could exist were predicted in 1956 by P. Kuroda.
• 1973 –Peter Mansfield formulates the physical theory ofnuclear magnetic resonance imaging (NMRI) akamagnetic resonance imaging (MRI).^{[52][53][54][55]}
• 1974 – Pier Giorgio Merli performs Young's double-slit experiment (1909) using a single electron with similar results, confirming the existence ofquantum fields for massive particles.
• 1977 –Ilya Prigogine develops non-equilibrium,irreversible thermodynamics andquantum operator theory, especially the timesuperoperator theory; he is awarded the Nobel Prize in Chemistry in 1977 "for his contributions to non-equilibrium thermodynamics, particularly the theory of dissipative structures".^[56]
• 1978 –Pyotr Kapitsa observes new phenomena in hot deuterium plasmas excited by very high power microwaves in attempts to obtain controlled thermonuclear fusion reactions in such plasmas placed in longitudinal magnetic fields, using a novel and low-cost design of thermonuclear reactor, similar in concept to that reported by Theodor V. Ionescuet al. in 1969. Receives a Nobel prize for early low temperature physics experiments on helium superfluidity carried out in 1937 at the Cavendish Laboratory in Cambridge, UK, and discusses his 1977 thermonuclear reactor results in his Nobel lecture on December 8, 1978.
• 1979 – Kenneth A. Rubinson and coworkers, at theCavendish Laboratory, observe ferromagneticspin wave resonant excitations in metallic glasses and interpret the observations in terms of two-magnon dispersion and aspin exchangeHamiltonian, similar in form to that of aHeisenberg ferromagnet.^[57]

• 1980 to 1982 –Alain Aspect verifies experimentally thequantum entanglement hypothesis; hisBell test experiments provide strong evidence that a quantum event at one location can affect an event at another location without any obvious mechanism for communication between the two locations.^[58][59] This remarkable result confirmed the experimental verification of quantum entanglement byJohn F. Clauser. and.Stuart Freedman in 1972.^[60] Aspect later shared the 2022Nobel Prize in Physics with Clauser andAnton Zeilinger "for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science".^[61]
• 1982 to 1997 –Tokamak Fusion Test Reactor (TFTR) atPPPL, Princeton, USA: Operated since 1982, produces 10.7 MW of controlled fusion power for only 0.21 s in 1994 by using T–D nuclear fusion in a tokamak reactor with "a toroidal 6T magnetic field for plasma confinement, a 3 MA plasma current and an electron density of1.0×10²⁰ m⁻³ of 13.5 keV"^[62]
• 1983 –Carlo Rubbia andSimon van der Meer, at theSuper Proton Synchrotron, see unambiguous signals ofW particles in January. The actual experiments are calledUA1 (led by Rubbia) andUA2 (led by Peter Jenni), and are the collaborative effort of many people.Simon van der Meer is the driving force on the use of the accelerator. UA1 and UA2 find theZ particle a few months later, in May 1983.
• 1983 to 2011 – The largest and most powerful experimental nuclear fusion tokamak reactor in the world,Joint European Torus (JET) begins operation at Culham Facility in UK; operates with T-D plasma pulses and has a reported gain factorQ of 0.7 in 2009, with an input of 40MW for plasma heating, and a 2800-ton iron magnet for confinement;^[63] in 1997 in a tritium-deuterium experiment JET produces 16 MW of fusion power, a total of 22 MJ of fusion, energy and a steady fusion power of 4 MW, which is maintained for 4 seconds.^[64]
• 1985 to 2010 – TheJT-60 (Japan Torus) begins operation in 1985 with an experimental D–D nuclear fusion tokamak similar to the JET; in 2010 JT-60 holds the record for the highest value of thefusion triple product achieved:1.77×10²⁸ K·s·m⁻³ =1.53×10²¹ keV·s·m⁻³.^[65] JT-60 claims it would have an equivalent energy gain factor,Q of 1.25 if it were operated with a T–D plasma instead of the D–D plasma, and on May 9, 2006, attains a fusion hold time of 28.6 s in full operation; moreover, a high-power microwavegyrotron construction is completed that is capable of 1.5 MW output for 1 s,^[66] thus meeting the conditions for the plannedITER, large-scale nuclear fusion reactor. JT-60 is disassembled in 2010 to be upgraded to a more powerful nuclear fusion reactor—the JT-60SA—by using niobium–titanium superconducting coils for the magnet confining the ultra-hot D–D plasma.
• 1986 –Johannes Georg Bednorz andKarl Alexander Müller produce unambiguous experimental proof ofhigh temperature superconductivity involvingJahn–Tellerpolarons in orthorhombic La₂CuO₄,YBCO and other perovskite-type oxides; promptly receive a Nobel prize in 1987 and deliver their Nobel lecture on December 8, 1987.^[67]
• 1986 –Vladimir Gershonovich Drinfeld introduces the concept ofquantum groups asHopf algebras in his seminal address on quantum theory at theInternational Congress of Mathematicians, and also connects them to the study of theYang–Baxter equation, which is a necessary condition for the solvability ofstatistical mechanics models; he also generalizes Hopf algebras toquasi-Hopf algebras, and introduces the study of Drinfeld twists, which can be used to factorize theR-matrix corresponding to the solution of theYang–Baxter equation associated with aquasitriangular Hopf algebra.
• 1988 to 1998 –Mihai Gavrilă discovers in 1988 the new quantum phenomenon ofatomic dichotomy in hydrogen and subsequently publishes a book on the atomic structure and decay in high-frequency fields of hydrogen atoms placed in ultra-intense laser fields.^{[68][69][70][71][72][73][74]}
• 1991 –Richard R. Ernst develops two-dimensional nuclear magnetic resonance spectroscopy (2D-FT NMRS) for small molecules in solution and is awarded the Nobel Prize in Chemistry in 1991 "for his contributions to the development of the methodology of high resolution nuclear magnetic resonance (NMR) spectroscopy".^[75]
• 1995 –Eric Cornell,Carl Wieman andWolfgang Ketterle and co-workers atJILA create the first "pure" Bose–Einstein condensate. They do this by cooling a dilute vapor consisting of approximately two thousand rubidium-87 atoms to below 170 nK using a combination of laser cooling and magnetic evaporative cooling. About four months later, an independent effort led by Wolfgang Ketterle atMIT creates a condensate made of sodium-23. Ketterle's condensate has about a hundred times more atoms, allowing him to obtain several important results such as the observation of quantum mechanical interference between two different condensates.
• 1997 –Peter Shor publishesShor's algorithm, a quantum computing algorithm for findingprime factors of integers.^[76] The algorithm is one of the few known quantum algorithms with immediate potential applications, which likely leads to asuperpolynomial improvement over known non-quantum algorithms.^[77]
• 1999 to 2013 – NSTX—TheNational Spherical Torus Experiment at PPPL, Princeton, USA launches a nuclear fusion project on February 12, 1999, for "an innovative magnetic fusion device that was constructed by the Princeton Plasma Physics Laboratory (PPPL) in collaboration with the Oak Ridge National Laboratory, Columbia University, and the University of Washington at Seattle"; NSTX is being used to study the physics principles of spherically shaped plasmas.^[78]

This section needs to beupdated. Please help update this article to reflect recent events or newly available information.(April 2024)

• 2001 – Researchers atIBM physically implementShor's algorithm with anNMR setup, factoring 15 into 3 times 5 using sevenqubits.^[79]
• 2002 –Leonid I. Vainerman organizes a meeting at Strasbourg of theoretical physicists and mathematicians focused on quantum group and quantum groupoid applications in quantum theories; the proceedings of the meeting are published in 2003 in a book edited by the meeting organizer.^[80]
• 2009 –Aaron D. O'Connell invents the firstquantum machine, applying quantum mechanics to a macroscopic object just large enough to be seen by the naked eye, which is able to vibrate a small amount and large amount simultaneously.^[81]
• 2011 –Zachary Dutton demonstrates how photons can co-exist in superconductors. "Direct Observation of Coherent Population Trapping in a Superconducting Artificial Atom",^[82]
• 2012 – The existence ofHiggs boson was confirmed by theATLAS andCMS collaborations based on proton-proton collisions in thelarge hadron collider at CERN.Peter Higgs andFrançois Englert were awarded the 2013 Nobel Prize in Physics for their theoretical predictions.^[83]
• 2015 – The firstloophole-free Bell tests are performed by three independent teams, lead byRonald Hanson andBas Hensen atTU Delft, bySae Woo Nam andKrister Shalm atNIST, and byAnton Zeilinger andMarissa Giustina at theUniversity of Vienna, confirming precisely the predictions of quantum mechanics and ruling out anylocal-realistic description of nature.^[84] These experiments are the culmination of a series of experiments started byJohn Clauser in the 1970s and significantly advanced byAlain Aspect in the 1980s among others. Clauser, Aspect, and Zeilinger share theNobel Prize in Physics 2022 for their results.^[85]

• Peacock, Kent A. (2008).The Quantum Revolution: A Historical Perspective. Westport, Conn.: Greenwood Press.ISBN 9780313334481.
• Ben-Menahem, A. (2009). "Historical timeline of quantum mechanics 1925–1989".Historical Encyclopedia of Natural and Mathematical Sciences (1st ed.). Berlin: Springer. pp. 4342–4349.ISBN 9783540688310.

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