History of quantum mechanics

The history of quantum mechanics, as it interlaces with the history of quantum chemistry, began essentially with a number of different scientific discoveries: the 1838 discovery of cathode rays by Michael Faraday; the 1859-1860 winter statement of the black body radiation problem by Gustav Kirchhoff; the 1877 suggestion by Ludwig Boltzmann that the energy states of a physical system could be discrete; the discovery of the photoelectric effect by Heinrich Hertz in 1887; and the 1900 quantum hypothesis by Max Planck that any energy-radiating atomic system can theoretically be divided into a number of discrete "energy elements" ε (epsilon) such that each of these energy elements is proportional to the frequency ν with which each of them individually radiate energy, as defined by the following formula:

$\epsilon = h \nu \,$

where h is a numerical value called Planck's constant.

Then, Albert Einstein in 1905, in order to explain the photoelectric effect previously reported by Heinrich Hertz in 1887, postulated consistently with Max Planck's quantum hypothesis that light itself is made of individual quantum particles, which in 1926 came to be called photons by Gilbert N. Lewis. The photoelectric effect was observed upon shining light of particular wavelengths on certain materials, such as metals, which caused electrons to be ejected from those materials only if the light quantum energy was greater than the Fermi level (work function) in the metal.

Ludwig Boltzmann’s diagram of the I₂ molecule proposed in 1898 showing the atomic “sensitive region” (α, β) of overlap

Niels Bohr's 1913 quantum model of the atom, which incorporated an explanation of Johannes Rydberg's 1888 formula, Max Planck's 1900 quantum hypothesis, i.e. that atomic energy radiators have discrete energy values (ε = hν), J. J. Thomson's 1904 plum pudding model, Albert Einstein's 1905 light quanta postulate, and Ernest Rutherford's 1907 discovery of the atomic nucleus

The phrase "quantum mechanics" was first used in Max Born's 1924 paper "Zur Quantenmechanik". In the years to follow, this theoretical basis slowly began to be applied to chemical structure, reactivity, and bonding.

Overview

In short, Ludwig Eduard Boltzmann was one of the founders of quantum mechanics because he suggested in 1877 that the energy levels of a physical system, such as a molecule, could be discrete. He was also a founder of the Austrian Mathematical Society together with the mathematicians Gustav von Escherich and Emil Müller. Boltzmann's rationale for the presence of discrete energy levels in molecules such as those of iodine gas had its origins in his statistical thermodynamics and statistical mechanics theories, and was backed up by mathematical arguments, as it will also be the case twenty years later with the first quantum theory put forward by Max Planck.

With decreasing temperature, the peak of the blackbody radiation curve shifts to longer wavelengths and also has lower intensities. The blackbody radiation curves (1862) at left are also compared with the early, classical limit model of Rayleigh and Jeans (1900) shown at right. The short wavelength side of the curves was already approximated in 1896 by the Wien distribution law.

Thus, in 1900, the German physicist Max Planck reluctantly introduced the idea that energy is quantized, to derive a formula for the observed frequency dependence of the energy emitted by a black body, called Planck's Law, that included a Boltzmann distribution (applicable in the classical limit). Planck's law can be stated as follows: $I(\nu,T) =\frac{ 2 h\nu^{3}}{c^2}\frac{1}{ e^{\frac{h\nu}{kT}}-1},$ where:

I(ν,T) is the energy per unit time (or the power) radiated per unit area of emitting surface in the normal direction per unit solid angle per unit frequency by a black body at temperature T;

h is the Planck constant;

c is the speed of light in a vacuum;

k is the Boltzmann constant;

ν is the frequency of the electromagnetic radiation; and T is the temperature of the body in degrees Kelvin.

The earlier Wien approximation may be derived from Planck's law by assuming $h\nu \gg kT$.

Moreover, the application of Planck's quantum theory to the electron allowed Ștefan Procopiu in 1911—1913, and subsequently Niels Bohr in 1913, to calculate the magnetic moment of the electron, which was later called the ``magneton"; similar quantum computations, but with numerically quite different values, were subsequently made possible for both the magnetic moments of the proton and the neutron that are three orders of magnitude smaller than that of the electron.

Photoelectric effect

The emission of electrons from a metal plate caused by light quanta (photons) with energy greater than the Fermi level of the metal.

The photoelectric effect reported by Heinrich Hertz in 1887,

and explained by Albert Einstein in 1905.

Low-energy phenomena: Photoelectric effect

Mid-energy phenomena: Compton scattering

High-energy phenomena: Pair production

In 1905, Einstein explained the photoelectric effect by postulating that light, or more generally all electromagnetic radiation, can be divided into a finite number of "energy quanta" that are localized points in space. From the introduction section of his March 1905 quantum paper, “On a heuristic viewpoint concerning the emission and transformation of light”, Einstein states:

``According to the assumption to be contemplated here, when a light ray is spreading from a point, the energy is not distributed continuously over ever-increasing spaces, but consists of a finite number of energy quanta that are localized in points in space, move without dividing, and can be absorbed or generated only as a whole."

This statement has been called the most revolutionary sentence written by a physicist of the twentieth century. These energy quanta later came to be called "photons", a term introduced by Gilbert N. Lewis in 1926. The idea that each photon had to consist of energy in terms of quanta was a remarkable achievement; it effectively solved the problem of black body radiation attaining infinite energy, which occurred in theory if light were to be explained only in terms of waves. In 1913, Bohr explained the spectral lines of the hydrogen atom, again by using quantization, in his paper of July 1913 On the Constitution of Atoms and Molecules.

These theories, though successful, were strictly phenomenological: during this time, there was no rigorous justification for quantization, aside, perhaps, from Henri Poincaré's discussion of Planck's theory in his 1912 paper Sur la théorie des quanta. They are collectively known as the old quantum theory.

The phrase "quantum physics" was first used in Johnston's Planck's Universe in Light of Modern Physics (1931).

In 1924, the French physicist Louis de Broglie put forward his theory of matter waves by stating that particles can exhibit wave characteristics and vice versa. This theory was for a single particle and derived from special relativity theory. Building on de Broglie's approach, modern quantum mechanics was born in 1925, when the German physicists Werner Heisenberg and Max Born developed matrix mechanics and the Austrian physicist Erwin Schrödinger invented wave mechanics and the non-relativistic Schrödinger equation as an approximation to the generalised case of de Broglie's theory. Schrödinger subsequently showed that the two approaches were equivalent.

Heisenberg formulated his uncertainty principle in 1927, and the Copenhagen interpretation started to take shape at about the same time. Starting around 1927, Paul Dirac began the process of unifying quantum mechanics with special relativity by proposing the Dirac equation for the electron. The Dirac equation achieves the relativistic description of the wavefunction of an electron that Schrödinger failed to obtain. It predicts electron spin and led Dirac to predict the existence of the positron. He also pioneered the use of operator theory, including the influential bra-ket notation, as described in his famous 1930 textbook. During the same period, Hungarian polymath John von Neumann formulated the rigorous mathematical basis for quantum mechanics as the theory of linear operators on Hilbert spaces, as described in his likewise famous 1932 textbook. These, like many other works from the founding period, still stand, and remain widely used.

The field of quantum chemistry was pioneered by physicists Walter Heitler and Fritz London, who published a study of the covalent bond of the hydrogen molecule in 1927. Quantum chemistry was subsequently developed by a large number of workers, including the American theoretical chemist Linus Pauling at Caltech, and John C. Slater into various theories such as Molecular Orbital Theory or Valence Theory.

Beginning in 1927, attempts were made to apply quantum mechanics to fields rather than single particles, resulting in what are known as quantum field theories. Early workers in this area included P.A.M. Dirac, W. Pauli, V. Weisskopf, and P. Jordan. This area of research culminated in the formulation of quantum electrodynamics by R.P. Feynman, F. Dyson, J. Schwinger, and S.I. Tomonaga during the 1940s. Quantum electrodynamics is a quantum theory of electrons, positrons, and the electromagnetic field, and served as a role model for subsequent Quantum Field theories.

Feynman diagram of gluon radiation in Quantum Chromodynamics

The theory of Quantum Chromodynamics was formulated beginning in the early 1960s. The theory as we know it today was formulated by Politzer, Gross and Wilczek in 1975.

Building on pioneering work by Schwinger, Higgs and Goldstone, the physicists Glashow, Weinberg and Salam independently showed how the weak nuclear force and quantum electrodynamics could be merged into a single electroweak force, for which they received the 1979 Nobel Prize in Physics.

Timeline

See also: Timeline of atomic and subatomic physics, Timeline of particle physics, and Timeline of physical chemistry

The following timeline shows the key steps, precursors and contributors to the development of quantum mechanics, quantum field theories and quantum chemistry:

Date	Person	Contributions
1877	Ludwig Eduard Boltzmann	Suggested that the energy levels of a physical system could be discrete based on statistical mechanics and mathematical arguments; also produced 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.
1887	Heinrich Hertz	Discovers the photoelectric effect, shown by Einstein in 1905 to involve quanta of light.
1888	Johannes Rydberg	Modified the Balmer formula to include all spectral series of lines for the hydrogen atom, producing the Rydberg formula which was employed later by Niels Bohr and others to verify Bohr's first quantum model of the atom.
1895	Wilhelm Conrad Röntgen	Discovered in December 1895 the X-rays in experiments with electron beams in plasma and received the first Nobel prize awarded in 1901; later, in 1922 in experiments involving scattering of X-rays by electrons, Arthur Compton demonstrated the "particle" aspect of electromagnetic radiation.
1896	Antoine Henri Becquerel	Discovered accidentally radioactivity while investigating the work of Wilhelm Conrad Röntgen; thus, he found that uranium salts emitted radiation that resembled Röntgen's X-rays in their penetrating power. In one experiment, Becquerel wrapped 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, prior to actually performing the experiment, Becquerel found that the photographic plates were already exposed, showing a projected image of his sample.
1896	Pieter Zeeman	First observed the Zeeman splitting effect by passing the light emitted by hydrogen through a magnetic field.
1899 to 1903	Ernest Rutherford, 1st Baron, Lord Rutherford of Nelson, of Cambridge, OM, FRS	During the investigation of radioactivity he coined the terms alpha and beta rays in 1899 to describe the two distinct types of radiation emitted by thorium and uranium salts. Ernest Rutherford was joined at McGill University in 1900 by Frederick Soddy and together they discovered nuclear transmutation when they found in 1902 that radioactive thorium was converting itself into radium through a process of nuclear decay and a gas (later found to be 4 2He); they reported their interpretation of radioactivity in 1903. Sir Ernest Rutherford became known as the ``father of nuclear physics": with his concept of the nuclear atom model proposed in 1911 he led the exploration of nuclear physics.
1900	Max Planck	To explain black body radiation (1862), he suggested that electromagnetic energy could only be emitted in quantized form, i.e. the energy could only be a multiple of an elementary unit E = hν, where h is Planck's constant and ν is the frequency of the radiation.
1902	Gilbert N. Lewis	To explain the octet rule (1893), he developed the “cubical atom” theory in which electrons in the form of dots were positioned at the corner of a cube and suggested 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 (1916).
1903	Antoine Henri Becquerel, Pierre Curie and Marie Curie, née Skłodowska, Becquerel's doctoral student	Shared the 1903 Nobel Prize in Physics for their discoveries and study of spontaneous radioactivity; Antoine Henri Becquerel accidentally discovered radioactivity in 1896 while investigating the phosphorescence of uranium salts. Then, Marie Skłodowska–Curie decided to look into uranium rays as a possible field of research for her doctoral thesis. She used to investigate her uranium salt samples a very sensitive electrometer device that was invented 15 years before by her husband and his brother Jacques Curie to measure electrical charge; using the Curie's electrometer, she discovered that rays emitted by the uranium salt samples caused the air around such samples to conduct electricity, and that the emitted rays' intensity could be quantitated using the Curie electrometer. In April 1898 she found through a systematic search of substances that thorium compounds, like those of uranium, emitted 'Becquerel rays', thus preceding the work of Frederick Soddy and Ernest Rutherford on the nuclear decay of thorium to radium by three years.
1904	Richard Abegg	Noted 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	Explained the photoelectric effect (reported in 1887 by Heinrich Hertz), i.e. that shining light on certain materials can function to eject electrons from the material, he postulated, as based on Planck’s quantum hypothesis (1900), that light itself consists of individual quantum particles (photons).
1905	Albert Einstein	First to explain the effects of Brownian motion as caused by the kinetic energy (i.e., movement) of atoms, which was subsequently, experimentally verified by Jean Baptiste Perrin, thereby settling the century-long dispute about the validity of John Dalton's atomic theory.
1905	Albert Einstein	Publishes his Special Theory of Relativity.
1905	Albert Einstein	Determines the equivalence of matter and energy.
1907 to 1917	Ernest Rutherford	To test his 'plum pudding' model of 1904, later known as the planetary, or Rutherford model, he sent a beam of positively-charged, alpha particles onto a gold foil and noticed that some bounced back thus showing that an atom has a small-sized positively charged atomic 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", 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 the Geiger-Marsden experiment by invoking a nuclear atom model and derived the Rutherford cross section.
1909	Geoffrey Ingram Taylor	Demonstrated that interference patterns of light were generated even when the light energy introduced consisted of only one photon. This discovery of the wave-particle duality of matter and energy was fundamental to the later development of quantum field theory.
1909 and 1916	Albert Einstein	Showed that, if Planck's law of black-body radiation is accepted, the energy quanta must also carry momentum p = h / λ, making them full-fledged particles.
1911	Lise Meitner and Otto Hahn	Performed an experiment that showed that the energies of electrons emitted by beta decay had a continuous rather than discrete spectrum. This was 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 was that the spin of the Nitrogen-14 atom was 1, in contradiction to the Rutherford prediction of ½. These anomalies were later explained by the discoveries of the neutrino and the neutron.
1911	Ștefan Procopiu	Performed experiments in which he determined the correct value of electron's magnetic dipole moment, μB = 9.27×10^(−21) erg·Oe^(−1); (in 1913 he was also able to calculate a theoretical value of the Bohr magneton based on Planck's quantum theory).
1912	Victor Hess	Discovers the existence of cosmic radiation.
1912	Henri Poincaré	Published an influential mathematical argument in support of the essential nature of energy quanta.
1913	Robert Andrews Millikan	Publishes the results of his "oil drop" experiment, in which he precisely determines the electric charge of the electron. Determination of the fundamental unit of electric charge made it possible to calculate the Avogadro constant (which is the number of atoms or molecules in one mole of any substance) and thereby to determine the atomic weight of the atoms of each element.
1913	Ștefan Procopiu	Publishes a theoretical paper with the correct value of the electron's magnetic dipole moment μB: Ştefan Procopiu. 1913. ``Determining the Molecular Magnetic Moment by M. Planck's Quantum Theory". Bulletin scientifique de l’Académie Roumaine de sciences., 1: 151.
1913	Niels Bohr	Obtains theoretically the value of the electron's magnetic dipole moment μB as a consequence of his atom model
1913	Johannes Stark and Antonino Lo Surdo	Independently discovered 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.
1913	Niels Bohr	To explain the Rydberg formula (1888), which correctly modeled the light emission spectra of atomic hydrogen, Bohr hypothesized 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.
1915	Albert Einstein	First presents to the Prussian Academy of Science what are now known as the Einstein 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's General Theory of Relativity. Although this theory is not directly applicable to quantum mechanics, theorists of quantum gravity seek to reconcile them.
1916	Arnold Sommerfeld	To account for the Zeeman effect (1896), i.e. that atomic absorption or emission spectral lines change when the light source is subjected to a magnetic field, he suggested there might be “elliptical orbits” in atoms in addition to spherical orbits.
1918	Sir Ernest Rutherford	Noticed that, when alpha particles were shot into nitrogen gas, his scintillation detectors showed the signatures of hydrogen nuclei. Rutherford determined that the only place this hydrogen could have come from was the nitrogen, and therefore nitrogen must contain hydrogen nuclei. He thus suggested that the hydrogen nucleus, which was known to have an atomic number of 1, was an elementary particle, which he decided must be the protons hypothesized by Eugen Goldstein.
1919	Irving Langmuir	Building on the work of Lewis (1916), he coined the term "covalence" and postulated that coordinate 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.
1921 and 1922	Frederick Soddy	Received 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 of isotopes"; he wrote 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 the spontaneous 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	Found that X-ray wavelengths increase due to scattering of the radiant energy by "free electrons". The scattered quanta have less energy than the quanta of the original ray. This discovery, known as the "Compton effect," or "Compton scattering" demonstrates the "particle" concept of electromagnetic radiation.
1922	Otto Stern and Walther Gerlach	Stern-Gerlach experiment detects discrete values of angular momentum for atoms in the ground state passing through an inhomogeneous magnetic field leading to the discovery of the spin of the electron.
1923	Louis De Broglie	Postulated that electrons in motion are associated with waves the lengths of which are given by Planck’s constant h divided by the momentum of the mv = p of the electron: λ = h / mv = h / p.
1924	Satyendra Nath Bose	His work on quantum mechanics provides the foundation for Bose-Einstein statistics, the theory of the Bose-Einstein condensate, and the discovery of the boson
1925	George Uhlenbeck and Samuel Goudsmit	Postulated the existence of the electron spin
1925	Friedrich Hund	Outlined the “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 in atomic orbitals and only the valence electrons needed to be in molecular orbitals involving both nuclei.
1925	Werner Heisenberg	Developed the matrix mechanics formulation of Quantum Mechanics.
1925	Wolfgang Pauli	Outlined the “Pauli exclusion principle” which states that no two identical fermions may occupy the same quantum state simultaneously.
1926	Gilbert N. Lewis	Coined the term photon, which he derived from the Greek word for light, φως (transliterated phôs).
1926	Oskar Klein and Walter Gordon (physicist)	Stated their relativistic quantum wave equation, now called the Klein-Gordon equation
1926	Enrico Fermi	Discovered the spin-statistics theorem connection
1926	Paul Dirac	Introduced Fermi-Dirac statistics
1926	Erwin Schrödinger	Used 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. directed valence bonds, which gave the correct values for spectral lines of the hydrogen atom; also introduced the Hamiltonian operator in quantum mechanics.
1926 to 1932	John von Neumann	Laid the mathematical foundations of Quantum Mechanics in terms of Hermitian operators on Hilbert spaces, subsequently published in 1932 as a basic textbook of quantum mechanics.
1927	Werner Heisenberg	Formulates the quantum uncertainty principle
1927	Max Born	interpreted the probabilistic nature of wavefunctions
1927	Walter Heitler and Fritz London	Introduced the concepts of valence bond theory and applied it to the hydrogen molecule.
1927	Thomas and Fermi	developed the Thomas-Fermi model
1927	Chandrasekhara Raman	Studied optical photon scattering by electrons
1927	Paul Dirac	Stated his relativistic electron quantum wave equation
1927	Charles G. Darwin and Walter Gordon	Solved the Dirac equation for a Coulomb potential
1927	Charles Drummond Ellis (along with James Chadwick and colleagues)	Finally established clearly that the beta decay spectrum is in fact continuous and not discrete, posing a problem that would later by solved by theorizing (and later discovering) the existence of the neutrino.
1927	Walter Heitler	Used Schrödinger’s wave equation (1926) to show how two hydrogen atom wavefunctions join together, with plus, minus, and exchange terms, to form a covalent bond.
1927	Robert Mulliken	In 1927 Mulliken worked, 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, introduced many new molecular orbital terminologies, such as σ bond, π bond, and δ bond.
1927	Hermann Klaus Hugo Weyl	Proved in collaboration with his student Fritz Peter a fundamental theorem in harmonic analysis—the Peter-Weyl theorem-- relevant to group representations in quantum theory (including the complete reducibility of unitary representations of a compact topological group); introduced the Weyl quantization, and earlier, in 1918, introduced the concept of gauge and a gauge theory; later in 1935 he introduced and characterized with Richard Bauer the concept of spinor in n-dimensions.
1928	Paul Dirac	In the Dirac equations, Paul Dirac integrated the principle of special relativity with quantum electrodynamics and hypothesized the existence of the positron.
1928	Linus Pauling	Outlined the nature of the chemical bond in which he used Heitler’s quantum mechanical covalent bond model (1927) to outline the quantum mechanical basis for all types of molecular structure and bonding and suggested 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.
1928	Friedrich Hund and Robert S. Mulliken	Introduce the concept of molecular orbital
1929	Oskar Klein	Discovers the Klein paradox
1929	Oskar Klein and Yoshio Nishina	Derive the Klein-Nishina cross section for high energy photon scattering by electrons
1929	Sir Nevill Mott	Derives the Mott cross section for the Coulomb scattering of relativistic electrons
1929	John Lennard-Jones	Introduced the linear combination of atomic orbitals approximation for the calculation of molecular orbitals.
1930	Paul Dirac	Introduces electron hole theory
1930	Fritz London	Explains van der Waals forces as due to the interacting fluctuating dipole moments between molecules
1930	Wolfgang Pauli	In a famous letter, Pauli suggested that, in addition to electrons and protons, atoms also contained an extremely light neutral particle which he called the "neutron." He suggested that this "neutron" was also emitted during beta decay and had simply not yet been observed. Later it was determined that this particle was actually the almost massless neutrino
1931	John Lennard-Jones	Proposes the Lennard-Jones interatomic potential
1931	Walther Bothe and Herbert Becker	Found that if the very energetic alpha particles emitted from polonium fell on certain light elements, specifically beryllium, boron, or lithium, an unusually penetrating radiation was produced. At first this radiation was thought to be gamma radiation, although it was more penetrating than any gamma rays known, and the details of experimental results were very difficult to interpret on this basis. Some scientists began to hypothesize the possible existence of another fundamental, atomic particle.
1931	Enrico Fermi	Renamed Pauli's "neutron" to neutrino to distinguish it from the then-hypothetical possibility of a much more massive neutron.
1932	Irène Joliot-Curie and Frédéric Joliot	Showed that if the unknown radiation generated by alpha particles fell on paraffin or any other hydrogen-containing compound, it ejected protons of very high energy. This was not in itself inconsistent with the proposed gamma ray nature of the new radiation, but detailed quantitative analysis of the data became increasingly difficult to reconcile with such a hypothesis.
1932	James Chadwick	Performed a series of experiments showing that the gamma ray hypothesis for the unknown radiation produced by alpha particles was untenable, and that the new particles must be the neutrons hypothesized by Enrico Fermi. Chadwick suggested that, in fact, the new radiation consisted of uncharged particles of approximately the same mass as the proton, and he performed a series of experiments verifying his suggestion.
1932	Werner Heisenberg	Applied perturbation theory to the two-electron problem and showed how resonance arising from electron exchange could explain exchange forces.
1932	Mark Oliphant	Building upon the nuclear transmutation experiments of Ernest Rutherford done a few years earlier, fusion of light nuclei (hydrogen isotopes) was first observed by Oliphant in 1932. The steps of the main cycle of nuclear fusion in stars were subsequently worked out by Hans Bethe throughout the remainder of that decade.
1932	Carl D. Anderson	Experimentally proves the existence of the positron.
1933	Leó Szilárd	First theorized the concept of a nuclear chain reaction. He filed a patent for his idea of a simple nuclear reactor the following year.
1934	Enrico Fermi	Published a very successful model of beta decay in which neutrinos were produced.
1934	Enrico Fermi	Studies the effects of bombarding uranium isotopes with neutrons.
1934	N.N.Semyonov	Develops the total quantitative chain chemical reaction theory. The idea of the chain reaction, developed by Semyonov, is the basis of various high technologies using the incineration of gas mixtures. The idea was also used for the description of the nuclear reaction.
1934	Irène Joliot-Curie and Frédéric Joliot-Curie	Discovered artificial radioactivity and were jointly awarded the 1935 Novel Prize in Chemistry
1935	Hideki Yukawa	Formulated his hypothesis of the Yukawa potential and predicted the existence of the pion, stating that such a potential arises from the exchange of a massive scalar 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 the fundamental forces necessitated massless particles.
1936	Alexandru Proca	Published prior to Hideki Yukawa his relativistic quantum field equations for a massive vector meson of spin-1 as a basis for nuclear forces.
1936	Garrett Birkhoff and John von Neumann	Introduced Quantum Logic in an attempt to reconcile the apparent inconsistency of classical, Boolean logic with the Heisenberg Uncertainty Principle of quantum mechanics as applied, for example, to the measurement of complementary (noncommuting) observables in quantum mechanics, such as position and momentum; current approaches to quantum logic involve noncommutative and non-associative many-valued logic.
1936	Carl D. Anderson	Discovered muons while he studied cosmic radiation.
1937	Carl Anderson	Experimentally proves the existence of the pion.
1937	Hermann Arthur Jahn and Edward Teller	Proved, using group theory, that non-linear degenerate molecules are unstable. The Jahn-Teller theorem essentially states that any non-linear molecule with a degenerate 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 the Jahn-Teller effect; this effect was recently considered also in relation to the superconductivity mechanism in YBCO and other high 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	Made the first accurate calculation of a molecular orbital wavefunction with the hydrogen molecule.
1938	Otto Hahn, Fritz Strassmann, Lise Meitner, and Otto Robert Frisch	Hahn and Strassmann sent a manuscript to Naturwissenschaften reporting they had detected the element barium after bombarding uranium with neutrons. Simultaneously, they communicated these results to Meitner. Meitner, and her nephew Frisch, correctly interpreted these results as being nuclear fission. Frisch confirmed this experimentally on 13 January 1939.
1939	Leó Szilárd and Enrico Fermi	Discovered neutron multiplication in uranium, proving that a chain reaction was indeed possible.
1942	Kan-Chang Wang	First proposed the use of beta capture to experimentally detect neutrinos.
1942	Enrico Fermi	Created the first artificial self-sustaining nuclear chain reaction, called Chicago Pile-1 (CP-1), in a racquets court below the bleachers of Stagg Field at the University of Chicago on December 2, 1942.
1945	Julius Robert Oppenheimer	Lead successfully the Manhattan Project, predicted quantum tunneling and proposed the Oppenheimer–Phillips process in nuclear fusion
1945	Manhattan Project	First nuclear fission explosion on July 16, 1945 in the Trinity test in New Mexico.
1946	Theodor V. Ionescu and Vasile Mihu	Reported the construction of the first hydrogen maser by coherent stimulation of radiation in molecular hydrogen.
1947	G. D. Rochester and C. C. Butler	Published two cloud chamber photographs of cosmic ray-induced events, one showing what appeared to be a neutral particle decaying into two charged pions, and one which appeared to be a charged particle decaying into a charged pion and something neutral. The estimated mass of the new particles was very rough, about half a proton's mass. More examples of these "V-particles" were slow in coming, and they were soon given the name kaons.
1948	Sin-Itiro Tomonaga and Julian Schwinger	Independently introduced perturbative renormalization as a method of correcting the original Lagrangian of a quantum field theory so as to eliminate an infinite series of counterterms that would otherwise result.
1948	Richard Feynman	Stated the path integral formulation of quantum mechanics.
1949	Freeman Dyson	Determined the equivalence of the formulations of quantum electrodynamics that existed by that time — Richard Feynman's diagrammatic path integral formulation and the operator method developed by Julian Schwinger and Sin-Itiro Tomonaga. A by-product of that demonstration was the invention of the Dyson series.
1951	Clemens C. J. Roothaan and George G. Hall	Derived the Roothaan-Hall equations, putting rigorous molecular orbital methods on a firm basis.
1951	Edward Teller--'Father of the Hydrogen bomb', physicist and Stanisław Ulam, mathematician	Were reported to have written jointly in March 1951 a classified report on “Hydrodynamic Lenses and Radiation Mirrors” that resulted in the next step in the Manhattan Project. In 1999, Edward Teller told a Scientific American reporter: "I contributed; Ulam did not. I'm sorry I had to answer it in this abrupt way. Ulam was rightly dissatisfied with an old approach. He came to me with a part of an idea which I already had worked out and (had) difficulty getting people to listen to. He was willing to sign a paper. When it then came to defending that paper and really putting work into it, he refused. He said: ``I don't believe in it".
1951 and 1952	Manhattan Project	First planned fusion thermonuclear reaction experiment was carried out successfully in the Spring of 1951 at Eniwetok, based only on the work of Edward Teller and Dr. Hans A. Bethe who wrote in 1952:``the results of the calculations of Ulam and Fermi in 1950 (which were logical steps in the program) would have led nearly every scientist to give up the thermonuclear program altogether. Only Teller's persistent belief in the practicality of thermonuclear reactions led to our present, completely novel concepts in this field.". The Los Alamos Laboratory proposed a date in November 1952 for a Hydrogen bomb, full-scale test that was apparently kept.
1951	Felix Bloch and Edward Mills Purcell	Received a shared Nobel Prize in Physics for their first observations of the quantum phenomenon of nuclear magnetic resonance reported in 1949 ("for their development of new methods for nuclear magnetic precision measurements and discoveries in connection therewith"); Felix Bloch reported his NMR discovery as "the Principle of Nuclear Induction" (in collaboration with W. W. Hansen, and M. Packard); Purcell reported his contribution as ``Research in Nuclear Magnetism", and gave credit to his coworkers such as Herbert S. Gutowsky for their NMR contributions, as well as theoretical researchers of nuclear magnetism such as Professor Van Vleck.
1952	Albert W. Overhauser	Formulated a theory of theory of the dynamic nuclear polarization, also known as the Overhauser Effect; other contenders are the subsequent theory of Ionel Solomon reported in 1955 that includes the Solomon equations for dipolar coupled spin dynamics, and that of R. Kaiser in 1963; Overhauser was elected to the US National Academy of Sciences in 1974 and received the National Medal of Science in 1994. The general Overhauser effect was first demonstrated experimentally by T. R. Carver and Charles P. Slichter in 1953
1953	Charles H. Townes,(collaborating with J. P. Gordon, and H. J. Zeiger)	Built and reported the first ammonia maser; received a Nobel prize in 1964 for his experimental success in producing coherent radiation by atoms and molecules.
1954	Chen Ning Yang and Robert Mills	Derived a gauge theory for nonabelian groups, leading to the successful formulation of both electroweak unification and quantum chromodynamics.
1955	Ionel Solomon	First nuclear magnetic resonance theory of magnetic dipole coupled nuclear spins and of the Nuclear Overhauser Effect (NOE).
1955 and 1956	Murray Gell-Mann and Kazuhiko Nishijima	Independently derived the Gell-Mann–Nishijima formula, which relates the baryon number B, the strangeness S, and the isospin Iz of hadrons to the charge Q, eventually leading to the systematic categorization of hadrons and, ultimately, the Quark Model of hadron composition.
1956	P. Kuroda	Predicted that self-sustaining nuclear chain reactions should occur in natural uranium deposits.
1956	Clyde L. Cowan and Frederick Reines	Experimentally proved the existence of the neutrino.
1957	John Bardeen, Leon Cooper and John Robert Schrieffer	Proposed their quantum BCS theory of low temperature superconductivity as a macroscopic quantum coherence phenomenon involving phonon coupled electron pairs with opposite spin, for which their received a Nobel prize in 1972.
1957	William Alfred Fowler, Margaret Burbidge, Geoffrey Burbidge, and Fred Hoyle	In their 1957 paper Synthesis of the Elements in Stars, they explained how the abundances of essentially all but the lightest chemical elements could be explained by the process of nucleosynthesis in stars.
1958 and 1976	Edward Raymond Andrew, FRS	Made critical field measurements on superconducting tin foils in 1949 for his PhD; then in 1958 he discovered the magic angle spinning (MAS) technique for obtaining resolved chemical shifts in solids, including Knight shifts in metals, and subsequently in 1964 carried out pioneering experiments with nuclear magnetic resonance imaging (NMRI) also in solids; for his important discoveries he was elected Fellow of the Royal Society in 1984; together with R.G. Eades he published an important theoretical paper on the separation of intramolecular and intermolecular contributions to the Van Vleck second moment of the NMR spectrum
1961	Clauss Jönsson	Performed Young's double-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	Published in 1961 the fundamental textbook on the quantum theory of Nuclear Magnetic Resonance entitled ``The Principles of Nuclear Magnetism". Clarendon Press: Oxford. pp. 599. OCLC 242700 (1961); it surpasses by far both the earlier textbook by E.R. Andrew published in 1955, and the Magnetic Resonance textbook published two years later by Professor Charles P. Slichter
1961	Sheldon Lee Glashow	Extended the electroweak unification models developed by Julian Schwinger by including a short range neutral current, the Z_o. The resulting symmetry structure that Glashow proposed, SU(2) X U(1), formed the basis of the accepted theory of the electroweak interactions.
1962	Leon M. Lederman, Melvin Schwartz and Jack Steinberger	Showed that more than one type of neutrino exists by detecting interactions of the muon neutrino (already hypothesised with the name "neutretto")
1962	Murray Gell-Mann and Yuval Ne'eman	Independently classified the hadrons according to a system that Gell-Mann called the "Eightfold Way," and which ultimately led to the quark model (1964) of hadron composition.
1962	Jeffrey Goldstone, Yoichiro Nambu, Abdus Salam, and Steven Weinberg	Developed what is now known as Goldstone's Theorem, in which it was proved that, if there is continuous symmetry transformation under which the Lagrangian is invariant, then either the vacuum state is also invariant under the transformation, or there must exist spinless particles of zero mass, thereafter called Nambu-Goldstone bosons. Subsequently, in 2004 Steven Weinberg explained in his 3-volume book on "Quantum Field Theory" that low temperature superconductivity could not be explained by the BCS model alone without the appearance of Goldstone bosons upon symmetry breaking. One notes however that the importance of symmetry breaking for superconductivity was already pointed out in 1973 by Brian David Josephson in his Nobel lecture.
1962 to 1973	Brian David Josephson, FRS	Predicted correctly the quantum tunnelling effect involving supercurrents while he was a PhD student under the supervision of Professor Brian Pippard at the Royal Society Mond Laboratory in Cambridge, UK; subsequently, in 1964, he applied his theory to coupled superconductors. The Josephson, tunnelling supercurrent effect was later demonstrated experimentally at Bell Labs in the USA. For his important quantum discovery he was awarded the Nobel Prize in Physics in 1973.
1963	Eugene P. Wigner	Laid the foundation for the theory of symmetries in quantum mechanics as well as for basic research into the structure of the atomic nucleus; made important "contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles"; he shared half of his Nobel prize in Physics with Maria Goeppert-Mayer and J. Hans D. Jensen.
1963	Maria Goeppert Mayer and J. Hans D. Jensen	Shared with Eugene P. Wigner one half of the Nobel Prize in Physics in 1963 "for their discoveries concerning nuclear shell structure theory".
1963	Nicola Cabibbo	Developed the mathematical matrix by which the first two (and ultimately three) generations of quarks could be predicted.
1964	Murray Gell-Mann and George Zweig	Independently proposed the quark model of hadrons, predicting the arbitrarily named up, down, and strange quarks. Gell-Mann is credited with coining the term "quark," which he found in James Joyce's book Finnegans Wake.
1964	François Englert, Robert Brout, Peter Higgs, Gerald Guralnik, C. R. Hagen, and Tom Kibble	Postulated that a fundamental quantum field, now called the Higgs field, permeates space and, by way of the Higgs mechanism, provides mass to all the elementary subatomic particles that interact with it. While the Higgs field is postulated to confer mass on quarks and leptons, it represents only a tiny portion of the masses of other subatomic particles, such as protons and neutrons. In these, gluons that bind quarks together confer most of the particle mass. The Higgs mechanism, which gives mass to vector bosons, such as Proca's vector spin-1 mesons, was theorized in 1964 by François Englert and Robert Brout. In October of the same year, Peter Higgs, working from the ideas of Philip Anderson reached the same conclusions; and, independently, by Gerald Guralnik, C. R. Hagen, and Tom Kibble, who worked out the results by the spring of 1963.
1964	Sheldon Lee Glashow and James Bjorken	Predicted the existence of the charm quark. The addition was proposed because it allowed for a better description of the weak interaction (the mechanism that allows quarks and other particles to decay), equalized the number of known quarks with the number of known leptons, and implied a mass formula that correctly reproduced the masses of the known mesons.
1964	Nikolai G. Basov and Aleksandr M. Prokhorov	Shared the Nobel Prize in Physics in 1964 for, respectively, semiconductor lasers and Quantum Electronics; they also shared the prize with Charles H. Townes, the inventor of the ammonium maser.
1967	Steven Weinberg and Abdus Salam	Published a paper in which he described Yang-Mills Theory using the SU(2) X U(1) supersymmetry group, thereby yielding a mass for the W particle of the Weak Interaction via spontaneous symmetry breaking.
1968	Stanford University	Deep inelastic scattering experiments at the Stanford Linear Accelerator Center (SLAC) showed that the proton contained much smaller, point-like objects and was therefore not an elementary particle. Physicists at the time were reluctant to identify these objects with quarks, instead calling them "partons" — a term coined by Richard Feynman. The objects that were observed at SLAC would later be identified as up and down quarks. Nevertheless, "parton" remains in use as a collective term for the constituents of hadrons (quarks, antiquarks, and gluons). The strange quark's existence was indirectly validated by the SLAC's scattering experiments: not only was it a necessary component of Gell-Mann and Zweig's three-quark model, but it provided an explanation for the kaon (K) and pion (π) hadrons discovered in cosmic rays in 1947.
1969 to 1977	Sir Neville Mott and Philip Warren Anderson	Published quantum theories for electrons in non-crystalline solids, such as glasses and amorphous semiconductors; received in 1977 a Nobel prize in Physics for their investigations into the electronic structure of magnetic and disordered systems,which allowed for the development of electronic switching and memory devices in computers; shared with John 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	Observed and reported quantum amplified stimulation of electromagnetic radiation in hot deuterium plasmas in a longitudinal magnetic field; published a quantum theory of the amplified coherent emission of radiowaves and microwaves by focused electron beams coupled to ions in hot plasmas.
1970	Sheldon Lee Glashow, John Iliopoulos and Luciano Maiani	Predicted the charmed quark that was subsequently found experimentally and shared a Nobel prize for their theoretical prediction.
1970	Anatole Abragam and B. Bleaney	Presented an extensive quantum theory of Electron Paramagnetic Resonance of transition ions with thoroughly worked out examples in an encyclopedic style that remains todate a key, enormous reference book; significantly, this unsurpassed quantum textbook, which is widely appreciated in the quantum mechanics community, was dedicated to J. H. Van Vleck.
1971	Martinus J. G. Veltman and Gerardus 't Hooft	Showed that, if the symmetries of Yang-Mills Theory were to be broken according to the method suggested by Peter Higgs, then Yang-Mills theory can be renormalized. The renormalization of Yang-Mills Theory predicted the existence of a massless particle, called the gluon, which could explain the nuclear Strong Force. It also explained how the particles of the Weak Interaction, the W and Z bosons, obtained their mass via spontaneous symmetry breaking and the Yukawa interaction.
1971	Jean Jeener, solid-state NMR physicist, professor	Introduced two-dimensional FT-NMR Spectroscopy at the Ampere Summer School in Basko Polje, Yugoslavia, in September 1971; his unpublished lecture notes for this presentation were later published in “NMR and More in Honour of Anatole Abragam”, Eds. M. Goldman and M. Porneuf, Les editions de physique, Avenue du Hoggar, Zone Industrielle de Courtaboeuf, BP 112, F-91944 Les Ulis cedex A, France (1994); ``it has shown an unprecedented impact on the development of state-of-the-art NMR spectroscopy. In principle, any multiple-dimensional NMR experiment introduced so far relies on the method proposed by Jean Jeener. Countless examples can be found in both liquid-state and solid-state NMR, as well as in NMR imaging applications in medicine, biology and material science".
1972	Francis Perrin	Discovered the existence of "natural nuclear fission reactors" in uranium deposits in Oklo, Gabon, where analysis of isotope ratios demonstrated that self-sustaining, nuclear chain reactions had occurred. The conditions under which a natural nuclear reactor could exist were predicted in 1956 by P. Kuroda.
1973	Frank Anthony Wilczek	Discovered the quark asymptotic freedom in the theory of strong interactions; received the Lorentz Medal in 2002, and the Nobel Prize in Physics in 2004 for his discovery and his subsequent contributions to Quantum Chromodynamics.
1973	Makoto Kobayashi and Toshihide Maskawa	Noted that the experimental observation of CP violation could be explained if an additional pair of quarks existed. The two new quarks were eventually named top and bottom.
1973	Peter Mansfield	Formulated the physical theory of Nuclear Magnetic Resonance Imaging (NMRI)
1974	Pier Giorgio Merli	Performed Young's double-slit experiment (1909) using a single electron with similar results, confirming the existence of quantum fields for massive particles.
1974	Burton Richter and Samuel Ting	Charm quarks were produced almost simultaneously by two teams in November 1974 (see November Revolution) — one at SLAC under Burton Richter, and one at Brookhaven National Laboratory under Samuel Ting. The charm quarks were observed bound with charm antiquarks in mesons. The two discovering parties had independently assigned the discovered meson two different symbols, J and ψ; thus, it became formally known as the J/ψ meson. The discovery finally convinced the physics community of the quark model's validity.
1975	Martin Lewis Perl	With his colleagues at the SLAC–LBL group, he detected the tau in a series of experiments between 1974 and 1977.
1977	Leon Lederman	Observed the bottom quark with his team at Fermilab. This discovery was a strong indicator of the top quark's existence: without the top quark, the bottom quark would have been without a partner that was required by the mathematics of the theory.
1977	Ilya Prigogine	Developed non-equilibrium, irreversible thermodynamics and quantum operator theory, especially the time superoperator theory; he was awarded the Nobel Prize in Chemistry in 1977 "for his contributions to non-equilibrium thermodynamics, particularly the theory of dissipative structures".
1978	Pyotr Kapitsa	Observed 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. Ionescu et al. in 1969; received a Nobel prize for early low temperature physics experiments on helium superfluidity carried out in 1937 at the Cavendish Laboratory in Cambridge, UK, and discussed his 1977 thermonuclear reactor results in his Nobel lecture on December 8, 1978.
1979	Kenneth A. Rubinson and coworkers	Observed at the Cavendish Laboratory ferromagnetic spin wave resonant excitations (FSWR) in locally anisotropic, FENiPB metallic glasses and interpreted the experimental results in terms of two-magnon dispersion and a spin exchange Hamiltonian, similar in form to that of a Heisenberg ferromagnet.
1980 to 1982	Alain Aspect	Verified experimentally the quantum entanglement hypothesis; his ``Bell test" experiments provided 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.
1982 to 1997	Tokamak Fusion Test Reactor(TFTR) at PPPL, Princeton, USA	Operated since 1982, produced 10.7MW of controlled fusion power for only 0.21s in 1994 by using T-D nuclear fusion in a tokamak reactor with ``a toroidal 6T magnetic field for plasma confinement, a 3MA plasma current and an electron density of 1.0 x 10**20 m-3 of 13.5keV"
1983	Carlo Rubbia and Simon van der Meer	Unambiguous signals of W particles were seen in January 1983 during a series of experiments conducted by Carlo Rubbia and Simon van der Meer at the Super Proton Synchrotron. The actual experiments were called UA1 (led by Rubbia) and UA2 (led by Peter Jenni), and were the collaborative effort of many people. Simon van der Meer was the driving force on the use of the accelerator. UA1 and UA2 found the Z particle a few months later, in May 1983.
1983 to 2011	JET	Began operation of the largest and most powerful, experimental nuclear fusion tokamak reactor in the world at Culham Facility in UK; operates with T-D plasma pulses and had a reported gain factor Q of 0.7 in 2009, with an input of 40MW for plasma heating, and a 2800 ton iron magnet for confinement; in 1997 in a tritium-deuterium experiment JET produced 16 MW of fusion power, a total of 22 MJ of fusion, energy and a steady fusion power of 4 MW which was maintained for 4 seconds.
1985 to 2010	JT-60 (Japan Torus)	Began operation in 1985 with an experimental D-D nuclear fusion tokamak similar to JET, currently run by the Japan Atomic Energy Agency's (JAEA) Naka Fusion Institute in the Ibaraki Prefecture; in 2010 JT-60 held the record for the highest value of the fusion triple product achieved: 1.77×1028 K·s·m−3 = 1.53×1021 keV·s·m−3.; JT-60 claimed an equivalent energy gain factor, Q of 1.25 if it would have been operated with a T-D plasma instead of the D-D plasma, and on May 9, 2006 attained a fusion hold time of 28.6 s in full operation; moreover, a high-power microwave gyrotron construction was completed which is capable of 1.5MW output for 1s, thus meeting the conditions for the planned ITER, large-scale nuclear fusion reactor;; JT-60 was disassembled in 2010 in order 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 and Karl Alexander Müller	Produced unambiguous experimental proof of high temperature superconductivity involving Jahn-Teller polarons in orthorhombic La_2CuO_4, YBCO and other perovskite-type oxides; promptly received a Nobel prize in 1987 and delivered their Nobel lecture on December 8, 1987.
1986	Vladimir Gershonovich Drinfel'd	Introduced the concept of 'quantum groups' as Hopf algebras in his seminal address on quantum theory at the International Congress of Mathematicians, and also connected them to the study of the Yang–Baxter equation, which is a necessary condition for the solvability of statistical mechanics models; he also generalized Hopf algebras to quasi-Hopf algebras, and introduced the study of Drinfeld twists, which can be used to factorize the R-matrix corresponding to the solution of the Yang–Baxter equation associated with a quasitriangular Hopf algebra.
1988 to 1998	Mihai Gavrilă	Discovered in 1988 the new quantum phenomenon of Atomic Dichotomy in hydrogen and subsequently published a book on the atomic structure and decay in high-frequency fields of hydrogen atoms placed in ultra-intense laser fields;.
1991	Richard R. Ernst	Developed Two-Dimensional Nuclear Magnetic Resonance Spectroscopy (2D-FT NMRS) for small molecules in solution and was 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".
1977 to 1995	Fermilab	The top quark was finally observed by a team at Fermilab after an 18-year search. It had a mass much greater than had been previously expected — almost as great as a gold atom.
1995	Eric Cornell, Carl Wieman and Wolfgang Ketterle	The first "pure" Bose–Einstein condensate was created by Eric Cornell, Carl Wieman, and co-workers at JILA. They did 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 at MIT created a condensate made of sodium-23. Ketterle's condensate had 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.
1998	Super-Kamiokande (Japan) detector facility	Reported experimental evidence for neutrino oscillations, implying that at least one neutrino has mass.
1999 to 2013	NSTX—The National Spherical Torus Experiment at PPPL, Princeton, USA	PPPL launched 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.
2000	CERN	CERN scientists publish experimental results in which they claim to have observed indirect evidence of the existence of a quark-gluon plasma, which they call a "new state of matter."
2001	The Sudbury Neutrino Observatory (Canada)	Confirmed the existence of neutrino oscillations.
2002	Leonid Vainerman	Organized at Strasbourg a meeting of theoretical physicists and mathematicians focused on quantum group and quantum groupoid applications in quantum theories; the proceedings of the meeting were published in 2003 in a book edited by the meeting organizer
2003	Sir Anthony James Leggett, KBE, FRS	Received the 2003 Nobel Prize in Physics for pioneering contributions to the quantum theory of superconductors, and superfluids such as Helium-3, shared with V. L. Ginzburg and A. A. Abrikosov.
2005	The RHIC accelerator of Brookhaven National Laboratory	Generated a quark-gluon fluid, perhaps the quark-gluon plasma
2007 to 2010	Charles Pence Slichter	Was awarded the National Medal of Science in 2007 for his studies of Nuclear Magnetic Resonance in Solids, and especially his NMR Studies of High-Temperature Superconductors.
2008 to 2010	Lithium Tokamak Experiment (LTX)	Started in September 2008—based on the Andrei Zakharov theory—using a very thin lithium metal layer (<40 microns) on the inside surface of a 'small' tokamak reactor—facing the ultra-hot plasma; it was however planned to achieve only 400kA plasma currents in 100 ms pulses in the Spring of 2009, but was expected to achieve higher plasma ignition temperatures than in other tokamaks that do not utilize the liquid lithium—plasma interface so that the lithium would "soak up the particles at the plasma edge", thus avoiding plasma cooling by hot plasma particles reflected at the walls, as shown in the earlier experiments with the CDX-U toroidal lithium tray where a 50% recycling coefficient was measured, that is 35% lower than in the TFTR; in CDX-U the measured thickness of the coating lithium layer was on the order of 10 nm; shut down for upgrades in 2010, including a neutral beam injector, and then to be re-started during 2011.
2007 to 2010	Alain Aspect, Anton Zeilinger and John Clauser	Presented progess with the resolution of the non-locality aspect of quantum theory and was awarded in 2010 the Wolf Prize in Physics, together with Anton Zeilinger and John Clauser
2010	Andre Geim and Konstantin Novoselov	Received the Nobel Prize in Physics ``for groundbreaking experiments regarding the two-dimensional material graphene" Graphene is a planar atomic-scale honeycomb lattice made of carbon atoms which exhibits unusual and interesting quantum properties. Energy states of the electrons with wavenumber k in graphene. Occupied states are shown in green and touch the unoccupied states (colored in blue) at the six k-vectors, without any gap between the two sets.

Founding experiments

• Thomas Young's double-slit experiment demonstrating the wave nature of light (c1805)
• Henri Becquerel discovers radioactivity (1896)
• J. J. Thomson's cathode ray tube experiments (discovers the electron and its negative charge) (1897)
• The study of black body radiation between 1850 and 1900, which could not be explained without quantum concepts.
• The photoelectric effect: Einstein explained this in 1905 (and later received a Nobel prize for it) using the concept of photons, particles of light with quantized energy
• Robert Millikan's oil-drop experiment, which showed that electric charge occurs as quanta (whole units), (1909)
• Ernest Rutherford's gold foil experiment disproved the plum pudding model of the atom which suggested that the mass and positive charge of the atom are almost uniformly distributed. (1911)
• Otto Stern and Walther Gerlach conduct the Stern-Gerlach experiment, which demonstrates the quantized nature of particle spin (1920)
• Clinton Davisson and Lester Germer demonstrate the wave nature of the electron in the Electron diffraction experiment (1927)
• Clyde L. Cowan and Frederick Reines confirm the existence of the neutrino in the neutrino experiment (1955)
• Claus Jönsson`s double-slit experiment with electrons (1961)
• The Quantum Hall effect, discovered in 1980 by Klaus von Klitzing. The quantized version of the Hall effect has allowed for the definition of a new practical standard for electrical resistance and for an extremely precise independent determination of the fine structure constant.
• The experimental verification of quantum entanglement by Alain Aspect in 1982.

See also

• Quantum
• History of quantum field theory
• Timeline of atomic and subatomic physics
• History of the molecule
• History of thermodynamics
• History of chemistry

	History of science portal
	Nuclear technology portal
	Physics portal

• Golden age of physics

Further reading

• Bacciagaluppi, Guido; Valentini, Antony (2009), Quantum theory at the crossroads: reconsidering the 1927 Solvay conference, Cambridge, UK: Cambridge University Press, pp. 9184, arXiv:quant-ph/0609184, Bibcode 2006quant.ph..9184B, ISBN 9780521814218, OCLC 227191829 
• Bernstein, Jeremy (2009), Quantum Leaps, Cambridge, Massachusetts: Belknap Press of Harvard University Press, ISBN 9780674035416, http://books.google.com/?id=j0Me3brYOL0C&printsec=frontcover 
• Jammer, Max (1966), The conceptual development of quantum mechanics, New York: McGraw-Hill, OCLC 534562 
• Jammer, Max (1974), The philosophy of quantum mechanics: The interpretations of quantum mechanics in historical perspective, New York: Wiley, ISBN 0471439584, OCLC 969760 
• F. Bayen, M. Flato, C. Fronsdal, A. Lichnerowicz and D. Sternheimer, Deformation theory and quantization I,and II, Ann. Phys. (N.Y.), 111 (1978) pp. 61–110, 111-151.
• D. Cohen, An Introduction to Hilbert Space and Quantum Logic, Springer-Verlag, 1989. This is a thorough and well-illustrated introduction.
• Finkelstein, D.. "Matter, Space and Logic". Boston Studies in the Philosophy of Science V: 1969. 
• A. Gleason. Measures on the Closed Subspaces of a Hilbert Space, Journal of Mathematics and Mechanics, 1957.
• R. Kadison. Isometries of Operator Algebras, Annals of Mathematics, Vol. 54, pp. 325–338, 1951
• G. Ludwig. Foundations of Quantum Mechanics, Springer-Verlag, 1983.
• G. Mackey. Mathematical Foundations of Quantum Mechanics, W. A. Benjamin, 1963 (paperback reprint by Dover 2004).
• R. Omnès. Understanding Quantum Mechanics, Princeton University Press, 1999. (Discusses logical and philosophical issues of quantum mechanics, with careful attention to the history of the subject).
• N. Papanikolaou. Reasoning Formally About Quantum Systems: An Overview, ACM SIGACT News, 36(3), pp. 51–66, 2005.
• C. Piron. Foundations of Quantum Physics, W. A. Benjamin, 1976.
• Hermann Weyl. The Theory of Groups and Quantum Mechanics, Dover Publications, 1950.

External links

• A History of Quantum Mechanics
• A Brief History of Quantum Mechanics
• Homepage of the Quantum History Project