Taken from Britney Spears Guide to Semiconductor Physics (which is linked below):
"Prince Louis De-Broglie, hypothesised that if waves could exhibit particle-like properties, then might particles also exhibit wave-like properties? This idea is expressed as particle-wave duality and allows us to give the electron a wave number k."
Quantum is the minimum amount of something - the minimum amount (portion) of an entity, which can't be divided any more.Also - the quanta are ''allowed'' values - that means that between the quanta exists values of the same entity which are not allowed and simply can't exist.
Principles of Quantum Mechanics was created in 1930.
The distinction is sometimes made to distinguish normal quantum mechanics (which does not incorporate special relativity) and quantum field theory (relativistic quantum mechanics). Since we know special relativity is correct it is the relativistic form of quantum mechanics which is true, but non-relativistic quantum mechanics is still used, because it is a good approximation at low energies and it is much simpler. Physics students typically study regular quantum mechanics before moving on to quantum field theory.
The concepts of quantum mechanics were not explored until the 20th century. Newton only lived into the 18th century, so Newton did no work on quantum mechanics.
The mixed state in quantum mechanics is the statistical ensemble of the pure states.
Quantum mechanics is a separate branch of physics. It is a general term given to all quantum physics. There are many subbranches, for example Quantum chronodynamics which describes the strong nuclear interaction.
Quantum Mechanics "replaced" Classical Mechanics in particle physics in mid-1930s.
The study of quantum mechanics can be quite difficult for some students.
There is no reasonable alternative to quantum mechanics, at least not something that can even compare with the predictive power and experimental accuracy as quantum theory. If you want to make predictions about things happening at small scales you cannot do without quantum mechanics. Also note that certain models which are now considered as possible theories of everything (e.g. string theory) all expand upon quantum mechanics, they do not make quantum mechanics invalid or unnecessary.
Quantum applied science is a young discipline of physics and technology, which transitions, some of the stranger characteristics of quantum mechanics, especially quantum entanglement and most recently quantum tunneling, into virtual applications such as quantum computing, quantum coding, quantum simulation, quantum metrology, quantum sensing, and quantum imaging.
I am not aware of it "not being explained". I would guess that you can explain the relevant aspects with quantum mechanics.
Quantum mechanics
Quantum mechanics is the description of the Universe, mainly on very small scales, as in subatomic particles. It has many weird aspects, that we are not accustomed to in our daily (large-scale) life.You can read an introduction to quantum mechanics, among other things, in the Wikipedia article "Introduction to quantum mechanics".