Quantum mechanics is the science of the very small that explains the behavior of matter and energy at the atomic and subatomic level. Some key aspects of quantum mechanics include wave-particle duality, Heisenberg's uncertainty principle, Schrodinger's wave equation, quantum superposition, quantum entanglement, and more. Many experiments such as the double slit experiment provide evidence of these quantum effects.

2. Contents

3. Introduction to Quantum Mechanics
Quantum mechanics is the science of the very
small. It explains the behavior of matter and its
interactions with energy on
the scale of atoms and subatomic particles.
Max Planck is regarded as the Father of
Quantum Theory
Max Planck

4. History of Quantum Mechanics
The history of quantum mechanics is a fundamental part
of the history of modern physics. Quantum mechanics'
history, as it interlaces with the history of quantum
chemistry, began essentially with a number of different
scientific discoveries such as cathode rays , Black-body
radiations, photoelectric effect etc.
But the real concept evolved after the introduction of
thermal radiation priciples of black bodies by Max
Planck. It further revolves around the nature of light and
intriguing properties of sub atomic particles.
Blackbody radiation Curve

5. QM as a Framework
 QM applied to Electromagnetism resulted in QED
 QM applied to strong interaction resulted in QCD
 QM applied to Photonics and Ray Optics resulted in Quantum Optics
 QM applied to gravitation resulted in Quantum Gravity

6. Double Slit Experiment
In this experiment, a coherent light source, such as a laser beam,
illuminates a plate pierced by two parallel slits, and the light passing
through the slits is observed on a screen behind the plate. The wave
nature of light causes the light waves passing through the two slits to
interfere, producing bright and dark bands on the screen — a result
that would not be expected if light consisted of classical particles.
However, the light is always found to be absorbed at the screen at
discrete points, as individual particles (not waves), the interference
pattern appearing via the varying density of these particle hits on the
screen. Furthermore, versions of the experiment that include detectors
at the slits find that each detected photon passes through one slit (as
would a classical particle), and not through both slits (as would a wave).
However, such experiments demonstrate that particles do not form the
interference pattern if one detects which slit they pass through. These
results demonstrate the principle of wave–particle duality.

7. Photoelectric effect
The photoelectric effect is the emission of electrons or other free carriers when light
shines on a material. Electrons emitted in this manner can be called photo electrons. This phenomenon
is commonly studied in electronic physics, as well as in fields of chemistry, such as quantum chemistry
or electrochemistry. The photons of a light beam have a characteristic energy proportional to the
frequency of the light. In the photoemission process, if an electron within some material absorbs the
energy of one photon and acquires more energy than the work function (the electron binding energy)
of the material, it is ejected. If the photon energy is too low, the electron is unable to escape the
material. Since an increase in the intensity of low-frequency light will only increase the number of low-
energy photons sent over a given interval of time, this change in intensity will not create any single
photon with enough energy to dislodge an electron. Thus, the energy of the emitted electrons does
not depend on the intensity of the incoming light, but only on the energy (equivalent frequency) of the
individual photons. It is an interaction between the incident photon and the outermost electrons.

8. Heisenberg’s Uncertainty Principle
In quantum mechanics, the uncertainty principle, also
known as Heisenberg's uncertainty principle or Heisenberg's
indeterminacy principle, is any of a variety of mathematical
inequalities asserting a fundamental limit to the precision with
which certain pairs of physical properties of a particle, known as
complementary variables, such as position x and momentum p,
can be known.

9. de Broglie Hypothesis
Louis de Broglie, in his
1924 PhD thesis, proposed that just
as light has both wave-like and
particle-like properties, electrons
also have wave-like properties. By
rearranging the momentum
equation stated in the above
section, we find a relationship
between the wavelength, λ
associated with an electron and its
momentum, p, through the Planck
constant h.

10. Schrödinger’s Wave Mechanics
In quantum mechanics, the Schrödinger equation is a
mathematical equation that describes the changes over time of a
physical system in which quantum effects, such as wave–particle
duality, are significant.
It is in general a linear partial differential equation, describing the
time-evolution of the system's wave function (also called a "state
function").

11. Quantum Superposition
Quantum superposition is a fundamental principle of
quantum mechanics. It states that, much like waves in classical
physics, any two (or more) quantum states can be added together
("superposed") and the result will be another valid quantum
state; and conversely, that every quantum state can be
represented as a sum of two or more other distinct states.
Mathematically, it refers to a property of solutions to the
Schrödinger equation; since the Schrödinger equation is linear,
any linear combination of solutions will also be a solution.

12. Quantum
Decoherence
Quantum decoherence is the loss of quantum coherence. In quantum mechanics,
particles such as electrons are described by a wavefunction, a mathematical description of
the quantum state of a system; the probabilistic nature of the wavefunction gives rise to
various quantum effects. As long as there exists a definite phase relation between different
states, the system is said to be coherent. This coherence is a fundamental property of
quantum mechanics, and is necessary for the functioning of quantum computers.
However, when a quantum system is not perfectly isolated, but in contact with its
surroundings, coherence decays with time, a process called quantum decoherence. As a
result of this process, the relevant quantum behaviour is lost.

13. Quantum Entanglement
Quantum entanglement is a physical phenomenon which occurs when pairs or
groups of particles are generated or interact in ways such that the quantum state of each
particle cannot be described independently of the state of the other(s), even when the
particles are separated by a large distance—instead, a quantum state must be described
for the system as a whole. Measurements of physical properties such as position,
momentum, spin, and polarization, performed on entangled particles are found to be
correlated.

14. Quantum Annealing
Quantum annealing (QA) is a metaheuristic for finding the global minimum
of a given objective function over a given set of candidate solutions (candidate
states), by a process using quantum fluctuations. Quantum annealing is used mainly
for problems where the search space is discrete (combinatorial optimization
problems) with many local minima; such as finding the ground state of a spin glass.
Quantum annealing starts from a quantum-mechanical superposition of all possible
states (candidate states) with equal weights. Then the system evolves following the
time-dependent Schrödinger equation, a natural quantum-mechanical evolution of
physical systems.

15. Josephson Junction
A Josephson junction is made by
sandwiching a thin layer of a
nonsuperconducting material between two layers
of superconducting material. The devices are
named after Brian Josephson, who predicted in
1962 that pairs of superconducting electrons
could "tunnel" right through the
nonsuperconducting barrier from one
superconductor to another. He also predicted the
exact form of the current and voltage relations
for the junction. Experimental work proved that
he was right, and Josephson was awarded the
1973 Nobel Prize in Physics for his work.