This timeline of quantum mechanics shows the
key steps, precursors and contributors to
the development of quantum mechanics, quantum
field theories and quantum chemistry.
== 19th century ==
1859 – Gustav Kirchhoff introduces the concept
of a blackbody and proves that its emission
spectrum depends only on its temperature.
1860–1900 – Ludwig Eduard Boltzmann, James
Clerk Maxwell and others develop the theory
of statistical mechanics. Boltzmann argues
that entropy is a measure of disorder.
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
of hydrogen, the Balmer series.
1887 – Heinrich Hertz discovers the photoelectric
effect, shown by Einstein in 1905 to involve
quanta of light.
1888 – Hertz demonstrates experimentally
that electromagnetic waves exist, as predicted
by Maxwell.
1888 – Johannes Rydberg modifies the Balmer
formula to include all spectral series of
lines for the hydrogen atom, producing the
Rydberg formula which is employed later by
Niels 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.
1896 – Antoine Henri Becquerel accidentally
discovers radioactivity while investigating
the work of Wilhelm 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.
1896-1897 – Pieter Zeeman first observes
the Zeeman splitting effect by applying a
magnetic field to light sources.
1896–1897 Marie Curie (née Skłodowska,
Becquerel's doctoral student) investigates
uranium salt samples using a very sensitive
electrometer 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 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.
1897 – Ivan Borgman demonstrates that X-rays
and radioactive materials induce thermoluminescence.
1897 – J. J. Thomson's experimentation with
cathode rays led him to suggest a fundamental
unit more than a 1,000 times smaller than
an atom, based on the high charge-to-mass
ratio. He called the particle a "corpuscle",
but later scientists preferred the term electron.
1899 to 1903 – Ernest Rutherford investigates
radioactivity. He coins the terms alpha and
beta rays in 1899 to describe the two distinct
types of radiation emitted by thorium and
uranium salts. Rutherford is joined at McGill
University in 1900 by Frederick Soddy and
together they discover nuclear transmutation
when they find in 1902 that radioactive thorium
is converting itself into radium through a
process of nuclear decay and a gas (later
found to be 42He); they report their interpretation
of radioactivity in 1903. Rutherford becomes
known as the "father of nuclear physics" with
his nuclear atom model of 1911.
== 20th century ==
=== 1900–1909 ===
1900 – To 
explain black-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
unit E = hν, where h is Planck's constant
and ν is the frequency of the radiation.
1902 – To explain the octet 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 on spontaneous 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 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 postulates, as based on Planck's quantum
hypothesis (1900), that light itself consists
of individual quantum particles (photons).
1905 – Einstein explains 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 – Einstein publishes his Special Theory
of Relativity.
1905 – Einstein theoretically derives the
equivalence of matter and energy.
1907 to 1917 – Ernest Rutherford: To test
his planetary model of 1904, later known as
the 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 demonstrates
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
is fundamental to the later development of
quantum field theory.
1909 and 1916 – Einstein shows 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.
=== 1910–1919 ===
1911 – Lise Meitner and Otto Hahn perform
an experiment that shows that the energies
of electrons emitted by beta 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 the Nitrogen-14 atom was
1, in contradiction to the Rutherford prediction
of ½. These anomalies are later explained
by the discoveries of the neutrino and the
neutron.
1911 – Ștefan Procopiu performs experiments
in which he determines the correct value of
electron's magnetic dipole moment, μB = 9.27×10−21
erg·Oe−1 (in 1913 he is 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 publishes 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 makes
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.
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 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.
1913 – To explain the Rydberg 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 and Gustav Hertz report
their experiment on electron collisions with
mercury atoms, which provides a new test of
Bohr's quantized model of atomic energy levels.
1915 – 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 – Paul Epstein and Karl Schwarzschild,
working independently, derive equations for
the linear and quadratic Stark effect in hydrogen.
1916 – Gilbert N. Lewis conceives the theoretical
basis of Lewis dot formulas, diagrams that
show the bonding between atoms of a molecule
and the lone pairs of electrons that may exist
in the molecule.
1916 – 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, Arnold Sommerfeld
suggests there might be "elliptical orbits"
in atoms in addition to spherical orbits.
1918 – Sir Ernest Rutherford notices that,
when alpha particles are shot into nitrogen
gas, his scintillation 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 an atomic number of
1, is an elementary particle, which he decides
must be the protons hypothesized by Eugen
Goldstein.
1919 – Building on the work of Lewis (1916),
Irving Langmuir coins the term "covalence"
and postulates 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.
=== 1920–1929 ===
1920 - Hendrik Kramers uses Bohr–Sommerfeld
quantization to derive formulas for intensities
of spectral transitions of the Stark effect.
Kramers also includes the effect of fine structure,
including corrections for relativistic kinetic
energy and coupling between electron spin
and orbit.
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 of isotopes"; 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 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 finds 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 perform
the Stern–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
the spin of the electron.
1922 – 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 the Auger
effect, where filling the inner-shell vacancy
of an atom is accompanied by the emission
of an electron from the same atom.
1923 – Louis de Broglie extends wave–particle
duality to particles, postulating that electrons
in motion are associated with waves. He predicts
that the wavelengths are given by Planck's
constant h divided by the momentum of the
mv = p of the electron: λ = h / mv = h / p.
1923 – Gilbert N. Lewis creates the theory
of Lewis acids and bases based on the properties
of electrons in molecules, defining an acid
as accepting an electron lone pair from a
base.
1924 – Satyendra Nath Bose explains Planck's
law using a new statistical law that governs
bosons, and Einstein generalizes it to predict
Bose–Einstein condensate. The theory becomes
known as Bose–Einstein statistics.
1924 – Wolfgang Pauli outlines the "Pauli
exclusion principle" which states that no
two identical fermions may occupy the same
quantum state simultaneously, a fact that
explains many features of the periodic table.
1925 – George Uhlenbeck and Samuel Goudsmit
postulate the existence of electron spin.
1925 – Friedrich Hund outlines Hund'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
in atomic orbitals and only the valence electrons
needed to be in molecular orbitals involving
both nuclei.
1925 – Werner Heisenberg, Max Born, and
Pascual Jordan develop the matrix mechanics
formulation of Quantum Mechanics.
1926 – Lewis coins the term photon in a
letter to the scientific journal Nature, which
he derives from the Greek word for light,
φως (transliterated phôs).
1926 – Oskar Klein and Walter Gordon state
their relativistic quantum wave equation,
later called the Klein–Gordon equation.
1926 – Enrico Fermi discovers the spin-statistics
theorem connection.
1926 – Paul Dirac introduces Fermi–Dirac
statistics.
1926 – 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. directed valence bonds, which gives the
correct values for spectral lines of the hydrogen
atom; also introduces the Hamiltonian operator
in quantum mechanics.
1926 – 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 by Hans Kramers.
1926 to 1932 – John von Neumann lays 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 develops the Copenhagen
interpretation of the probabilistic nature
of wavefunctions.
1927 – Born and J. Robert Oppenheimer introduce
the Born–Oppenheimer approximation, which
allows the quick approximation of the energy
and wavefunctions of smaller molecules.
1927 – Walter Heitler and Fritz London introduce
the concepts of valence bond theory and apply
it to the hydrogen molecule.
1927 – Thomas and Fermi develop the Thomas–Fermi
model for a Gas in a box.
1927 – Chandrasekhara Venkata Raman studies
optical photon scattering by electrons.
1927 – Dirac states his relativistic electron
quantum wave equation, the Dirac equation.
1927 – Charles Galton Darwin and Walter
Gordon solve the Dirac equation for a Coulomb
potential.
1927 – Charles Drummond Ellis (along with
James 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 the
neutrino.
1927 – Walter Heitler uses Schrödinger's
wave equation to show how two hydrogen atom
wavefunctions join together, with plus, minus,
and exchange terms, to form a covalent bond.
1927 – 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 as σ bond, π bond, and
δ bond.
1927 – Eugene Wigner relates degeneracies
of quantum states to irreducible representations
of symmetry groups.
1927 – Hermann Klaus Hugo Weyl proves 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); introduces the
Weyl quantization, and earlier, in 1918, introduces
the concept of gauge and a gauge theory; later
in 1935 he introduces and characterizes with
Richard Bauer the concept of spinor in n-dimensions.
1928 – Linus Pauling outlines the nature
of the chemical bond: uses Heitler's quantum
mechanical covalent bond model to outline
the quantum 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.
1928 – Friedrich Hund and Robert S. Mulliken
introduce the concept of molecular orbitals.
1928 – Born and Vladimir Fock formulate
and prove the adiabatic theorem, which states
that a physical system shall remain in its
instantaneous eigenstate if a given perturbation
is acting on it slowly enough and if there
is a gap between the eigenvalue and the rest
of the Hamiltonian's spectrum.
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 introduces the
linear combination of atomic orbitals approximation
for the calculation of molecular orbitals.
1929 – Fritz Houtermans and Robert d'Escourt
Atkinson propose that stars release energy
by nuclear fusion.
=== 1930–1939 ===
1930 – Dirac hypothesizes the existence
of the positron.
1930 – Dirac's textbook Principles of Quantum
Mechanics is published, becoming a standard
reference book that is still used today.
1930 – Erich Hückel introduces the Hückel
molecular orbital method, which expands on
orbital theory to determine the energies of
orbitals of pi electrons in conjugated hydrocarbon
systems.
1930 – Fritz London explains van der Waals
forces as due to the interacting fluctuating
dipole moments between molecules
1930 – Pauli suggests in a famous letter
that, in addition to electrons and protons,
atoms also contain an extremely light neutral
particle which 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.
1931 – John Lennard-Jones proposes the Lennard-Jones
interatomic potential
1931 – Walther Bothe and Herbert Becker
find that if the very energetic alpha particles
emitted from polonium fall on certain light
elements, specifically beryllium, boron, or
lithium, an unusually penetrating radiation
is produced. At first this radiation is thought
to be gamma 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.
1931 – Erich Hückel redefines the property
of aromaticity in a quantum mechanical context
by introducing the 4n+2 rule, or Hückel's
rule, which predicts whether an organic planar
ring molecule will have aromatic properties.
1931 – Ernst Ruska creates the first electron
microscope.
1931 – Ernest Lawrence creates the first
cyclotron and founds the Radiation Laboratory,
later the Lawrence Berkeley National Laboratory;
in 1939 he awarded the Nobel Prize in Physics
for his work on the cyclotron.
1932 – Irène Joliot-Curie and Frédéric
Joliot show that if the unknown radiation
generated by alpha particles falls on paraffin
or any other hydrogen-containing compound,
it ejects protons of very high energy. This
is not in itself inconsistent with the proposed
gamma ray nature of the new radiation, but
detailed quantitative analysis of the data
become increasingly difficult to reconcile
with such a hypothesis.
1932 – 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 the neutrons hypothesized
by Fermi.
1932 – Werner Heisenberg applies perturbation
theory to the two-electron problem to show
how resonance arising from electron exchange
can explain exchange forces.
1932 – 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.
1932 – Carl D. Anderson experimentally proves
the existence of the positron.
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 successful
model of beta decay in which neutrinos are
produced.
1934 – Fermi studies the effects of bombarding
uranium isotopes with neutrons.
1934 – 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.
1934 – Irène Joliot-Curie and Frédéric
Joliot-Curie discover artificial radioactivity
and are jointly awarded the 1935 Nobel Prize
in Chemistry
1935 – Einstein, Boris Podolsky, and Nathan
Rosen describe the EPR paradox which challenges
the completeness of quantum mechanics as it
was theorized up to that time. Assuming that
local realism is valid, they demonstrated
that there would need to be hidden parameters
to explain how measuring the quantum state
of one particle could influence the quantum
state of another particle without apparent
contact between them.
1935 - Schrödinger develops the Schrödinger's
cat thought experiment. It illustrates what
he saw as the problems of the Copenhagen interpretation
of quantum mechanics if subatomic particles
can be in two contradictory quantum states
at once.
1935 – Hideki Yukawa formulates his hypothesis
of the Yukawa potential and predicts 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 publishes 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
introduce 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 discovers muons
while he is studying cosmic radiation.
1937 – Hermann Arthur Jahn and Edward Teller
prove, 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 makes the first accurate
calculation of a molecular orbital wavefunction
with the hydrogen molecule.
1938 – Otto Hahn and his assistant Fritz
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 to Lise Meitner.
Meitner, and her nephew Otto Robert Frisch,
correctly interpret these results as being
a nuclear 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.
=== 1940–1949 ===
1942 – Kan-Chang Wang first proposes the
use of K-electron capture to experimentally
detect neutrinos.
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 the Manhattan Project, predicts quantum
tunneling and proposes the Oppenheimer–Phillips
process in nuclear fusion
1945 – the Manhattan Project produces the
first nuclear fission explosion on July 16,
1945 in the Trinity test in New Mexico.
1945 – John Archibald Wheeler and Richard
Feynman originate Wheeler–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 first hydrogen
maser by stimulated emission of radiation
in molecular hydrogen.
1947 – Willis Lamb and Robert Retherford
measure a small difference in energy between
the energy levels 2S1/2 and 2P1/2 of the hydrogen
atom, known as the Lamb shift.
1947 – George Rochester and Clifford Charles
Butler publishes two cloud 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 name kaons.
1948 – Sin-Itiro Tomonaga and Julian Schwinger
Independently introduce perturbative renormalization
as a method of correcting the original Lagrangian
of a quantum field theory so as to eliminate
a series of infinite terms that would otherwise
result.
1948 – Richard Feynman states the path integral
formulation of quantum mechanics.
1949 – Freeman Dyson determines the equivalence
of two formulations of quantum electrodynamics:
Feynman's diagrammatic path integral formulation
and the operator method developed by Julian
Schwinger and Tomonaga. A by-product of that
demonstration is the invention of the Dyson
series.
=== 1950–1959 ===
1951 – Clemens C. J. Roothaan and George
G. Hall derive the Roothaan-Hall equations,
putting rigorous molecular orbital methods
on a firm basis.
1951 – Edward Teller, physicist and "father
of the hydrogen bomb", and Stanislaw 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.
1951 and 1952 – at the Manhattan Project,
the first planned fusion thermonuclear 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.
The Los Alamos Laboratory proposes a date
in November 1952 for a hydrogen bomb, full-scale
test that is apparently carried out.
1951 – Felix Bloch and Edward Mills Purcell
receive a shared Nobel Prize in Physics for
their first observations of the quantum phenomenon
of nuclear magnetic resonance previously reported
in 1949. Purcell reports his contribution
as Research in Nuclear Magnetism, and gives
credit to his coworkers such as Herbert S.
Gutowsky for their NMR contributions, as well
as theoretical researchers of nuclear magnetism
such as John Hasbrouck Van Vleck.
1952 – Albert W. Overhauser formulates a
theory of 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 the dynamics of coupled spins,
and that of R. Kaiser in 1963. The general
Overhauser effect is first demonstrated experimentally
by T. R. Carver and Charles P. Slichter in
1953.
1952 – Donald A. Glaser creates the bubble
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 of
their helical paths. Glaser receives a Nobel
prize in 1960 for his invention.
1953 – Charles H. Townes, collaborating
with James P. Gordon, and H. J. Zeiger, builds
the first ammonia maser; receives a Nobel
prize in 1964 for his experimental success
in producing coherent radiation by atoms and
molecules.
1954 – Chen Ning Yang and Robert Mills derive
a gauge theory for nonabelian groups, leading
to the successful formulation of both electroweak
unification and quantum chromodynamics.
1955 – Ionel Solomon develops the first
nuclear magnetic resonance theory of magnetic
dipole coupled nuclear spins and of the Nuclear
Overhauser Effect.
1955 and 1956 – Murray Gell-Mann and Kazuhiko
Nishijima independently derive the Gell-Mann–Nishijima
formula, which relates the baryon number,
the strangeness, and the isospin of hadrons
to the charge, eventually leading to the systematic
categorization of hadrons and, ultimately,
the Quark Model of hadron composition.
1956 – P. Kuroda predicts that self-sustaining
nuclear chain reactions should occur in natural
uranium deposits.
1956 – Chien-Shiung Wu carries out the Wu
Experiment, which observes parity violation
in cobalt-60 decay, showing that parity violation
is present in the weak interaction.
1956 – Clyde L. Cowan and Frederick Reines
experimentally prove the existence of the
neutrino.
1957 – John Bardeen, Leon Cooper and John
Robert Schrieffer propose their quantum BCS
theory of low temperature superconductivity,
for which their receive a Nobel prize in 1972.
The theory represents superconductivity as
a macroscopic quantum coherence phenomenon
involving phonon coupled electron pairs with
opposite spin
1957 – William Alfred Fowler, Margaret Burbidge,
Geoffrey Burbidge, and Fred Hoyle, in their
1957 paper Synthesis of the Elements in Stars,
show that the abundances of essentially all
but the lightest chemical elements can be
explained by the process of nucleosynthesis
in stars.
1957 – Hugh Everett formulates the many-worlds
interpretation of quantum mechanics, which
states that every possible quantum outcome
is realized in divergent, non-communicating
parallel universes in quantum superposition.
1958–1959 – magic angle spinning described
by Edward Raymond Andrew, A. Bradbury, and
R. G. Eades, and independently in 1959 by
I. J. Lowe.
=== 1960–1969 ===
1961 – Clauss Jönsson performs 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 publishes the fundamental
textbook on the quantum theory of Nuclear
Magnetic Resonance entitled The Principles
of Nuclear Magnetism;
1961 – Sheldon Lee Glashow extends the electroweak
interaction models developed by Julian Schwinger
by including a short range neutral current,
the Z_o. The resulting symmetry structure
that Glashow proposes, SU(2) X U(1), forms
the basis of the accepted theory of the electroweak
interactions.
1962 – Leon M. Lederman, Melvin Schwartz
and Jack Steinberger show 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 classify 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 develop what
is now known as Goldstone'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 called
Nambu-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.
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 with Maria Goeppert-Mayer
and J. Hans D. Jensen.
1963 – Maria Goeppert Mayer and J. Hans
D. Jensen share with Eugene P. Wigner half
of the Nobel Prize in Physics in 1963 "for
their discoveries concerning nuclear shell
structure theory".
1963 – Nicola Cabibbo develops the mathematical
matrix by which the first two (and ultimately
three) generations of quarks can be predicted.
1964 – Murray Gell-Mann and George Zweig
independently propose 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 postulate 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 result is obtained independently
by three groups: François Englert and Robert
Brout; Peter Higgs, working from the ideas
of Philip Anderson; and Gerald Guralnik, C.
R. Hagen, and Tom Kibble.
1964 – Sheldon Lee Glashow and James Bjorken
predict the existence of the charm quark.
The addition is proposed because it allows
for a better description of the weak interaction
(the mechanism that allows quarks and other
particles to decay), equalizes the number
of known quarks with the number of known leptons,
and implies a mass formula that correctly
reproduced the masses of the known mesons.
1964 – John Stewart Bell puts forth Bell's
theorem, which used testable inequality relations
to show the flaws in the earlier Einstein–Podolsky–Rosen
paradox and prove that no physical theory
of local hidden variables can ever reproduce
all of the predictions of quantum mechanics.
This inaugurated the study of quantum entanglement,
the phenomenon in which separate particles
share the same quantum state despite being
at a distance from each other.
1964 – Nikolai G. Basov and Aleksandr M.
Prokhorov share the Nobel Prize in Physics
in 1964 for, respectively, semiconductor lasers
and Quantum Electronics; they also share the
prize with Charles Hard Townes, the inventor
of the ammonium maser.
1967 – Steven Weinberg and Abdus Salam publish
a paper in which he describes 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) show that the proton
contains much smaller, point-like objects
and is therefore not an elementary particle.
Physicists at the time are reluctant to identify
these objects with quarks, instead calling
them partons — a term coined by Richard
Feynman. The objects that are observed at
SLAC will 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 existence of the strange quark is indirectly
validated by the SLAC's scattering experiments:
not only is it a necessary component of Gell-Mann
and Zweig's three-quark model, but it provides
an explanation for the kaon (K) and pion (π)
hadrons discovered in cosmic rays in 1947.
1969 to 1977 – Sir Nevill Mott and Philip
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 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 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.
1970 – Glashow, John Iliopoulos and Luciano
Maiani predict the charmed quark that is subsequently
found experimentally and share a Nobel prize
for their theoretical prediction.
=== 1971–1979 ===
1971 – Martinus J. G. Veltman and Gerardus
't Hooft show that, if the symmetries of Yang–Mills
theory are broken according to the method
suggested by Peter Higgs, then Yang–Mills
theory can be renormalized. The renormalization
of Yang–Mills Theory predicts the existence
of a massless particle, called the gluon,
which could explain the nuclear strong force.
It also explains how the particles of the
weak interaction, the W and Z bosons, obtain
their mass via spontaneous symmetry breaking
and the Yukawa interaction.
1972 – Francis Perrin discovers "natural
nuclear fission reactors" in uranium deposits
in Oklo, 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 – Frank Anthony Wilczek discover the
quark asymptotic freedom in the theory of
strong interactions; receives 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
note that the experimental observation of
CP violation can be explained if an additional
pair of quarks exist. The two new quarks are
eventually named top and bottom.
1973 – Peter Mansfield formulates the physical
theory of Nuclear magnetic resonance imaging
(NMRI)
1974 – Pier Giorgio Merli performs 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 are 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 are observed
bound with charm antiquarks in mesons. The
two discovering parties independently assign
the discovered meson two different symbols,
J and ψ; thus, it becomes formally known
as the J/ψ meson. The discovery finally convinces
the physics community of the quark model's
validity.
1975 – Martin Lewis Perl, with his colleagues
at the SLAC–LBL group, detects the tau in
a series of experiments between 1974 and 1977.
1977 – Leon Lederman observes the bottom
quark with his team at Fermilab. This discovery
is a strong indicator of the top quark's existence:
without the top quark, the bottom quark would
be without a partner that is required by the
mathematics of the theory.
1977 – Ilya Prigogine develops non-equilibrium,
irreversible thermodynamics and quantum operator
theory, especially the time superoperator
theory; he is awarded the Nobel Prize in Chemistry
in 1977 "for his contributions to non-equilibrium
thermodynamics, particularly the theory of
dissipative structures".
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. Ionescu et 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 the Cavendish Laboratory, observe ferromagnetic
spin wave resonant excite journals (FSWR)
in locally anisotropic, FENiPB metallic glasses
and interpret the observations in terms of
two-magnon dispersion and a spin exchange
Hamiltonian, similar in form to that of a
Heisenberg ferromagnet.
=== 1980–1999 ===
1980 to 1982 – Alain Aspect verifies experimentally
the quantum entanglement hypothesis; his Bell
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.
1982 to 1997 – Tokamak Fusion Test Reactor
(TFTR) at PPPL, Princeton, USA: Operated since
1982, produces 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 1.0×1020 m−3 of 13.5 keV"
1983 – Carlo Rubbia and Simon van der Meer,
at the Super Proton Synchrotron, see unambiguous
signals of W particles in January. The actual
experiments are called UA1 (led by Rubbia)
and UA2 (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 the Z
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 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 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.
1985 to 2010 – The JT-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 the fusion triple product achieved:
1.77×1028 K·s·m−3 = 1.53×1021 keV·s·m−3.;
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
microwave gyrotron construction is completed
that is capable of 1.5MW output for 1s, thus
meeting the conditions for the planned ITER,
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 and Karl Alexander
Müller produce unambiguous experimental proof
of high temperature superconductivity involving
Jahn-Teller polarons 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.
1986 – Vladimir Gershonovich Drinfeld introduces
the concept of quantum groups as Hopf algebras
in his seminal address on quantum theory at
the International Congress of Mathematicians,
and also connects them to the study of the
Yang–Baxter equation, which is a necessary
condition for the solvability of statistical
mechanics models; he also generalizes Hopf
algebras to quasi-Hopf algebras, and introduces
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 discovers
in 1988 the new quantum phenomenon of atomic
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.
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."
1977 to 1995 – The top quark is finally
observed by a team at Fermilab after an 18-year
search. It has a mass much greater than had
been previously expected — almost as great
as a gold atom.
1995 – Eric Cornell, Carl Wieman and Wolfgang
Ketterle and co-workers at JILA 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 at MIT 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.
1998 – The Super-Kamiokande (Japan) detector
facility reports 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 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.
== 21st century ==
2000 – scientists at European Organization
for Nuclear Research (CERN) 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) confirm the existence of neutrino
oscillations. Lene Hau stops a beam of light
completely in a Bose–Einstein condensate.
2002 – Leonid 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.
2003 – Sir Anthony James Leggett receives
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 generates a quark-gluon
fluid, perhaps the quark–gluon plasma
2007 to 2010 – Charles Pence Slichter is
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.
2007 to 2010 – Alain Aspect, Anton Zeilinger
and John Clauser present progress with the
resolution of the non-locality aspect of quantum
theory and in 2010 are awarded the Wolf Prize
in Physics, together with Anton Zeilinger
and John Clauser.
2009 - Aaron D. O'Connell invents the first
quantum 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.
2011 - Zachary Dutton demonstrates how photons
can co-exist in superconductors. "Direct Observation
of Coherent Population Trapping in a Superconducting
Artificial Atom",
2014 – Scientists transfer data by quantum
teleportation over a distance of 10 feet with
zero percent error rate, a vital step towards
a quantum internet.
== See also
