# quantum physics

*Published: 07-06-2021 - Last Edited: 04-04-2023*

*by*George Meyer

## What is Quantum mechanics? What is its field of study? Moreover, what is it used for?

What exactly is the definition of Quantum physics? Quantum physics covers all the fields of physics. This is where the use of the laws of quantum mechanics is necessary to understand the phenomena at stake. Quantum mechanics is the fundamental theory of the particles of matter which constitute the universe’s objects and the force fields animating these objects.

### A framework of physical laws from the infinitely small to the infinitely large

Combined with special relativity, quantum mechanics has allowed us to build the standard model of elementary particles from quantum field theory. It is an attempt to unify the laws of quantum mechanics with general relativity.

The theory of quantum gravitation is still under construction. However, the two most promising attempts are the theory of superstrings and loop quantum gravitation. They allow us to do quantum cosmology, which is also still under development. Contrary to the standard model -confirmed by experiments such as discovering the W bosons and the Brout-Englert-Higgs boson- there is no evidence to support quantum gravitation theories.

## The quantum definition

When we consider the quantum definition, we see two of the most famous equations governing the quantum world. This is the Schrödinger equation (top), recognized in quantum mechanics, with the Heisenberg inequalities below. The background image is of particles spiraling in a bubble chamber immersed in a magnetic field. At the bottom right, a Feynman diagram illustrates the beta decay of a neutron (n) into a proton (p) wallchan.com

The theory behind quantum physics is highly mathematical and very subtle in terms of concepts. There is a broad spectrum of physical interpretations of quantum mechanics beyond the orthodox Copenhagen interpretation. Quantum mechanics gives an outstanding and not very intuitive description of particles, electrons, or photons. For example, which is a sure way to understand there are also waves. They can be found simultaneously in two places or across obstacles, seemingly impassable (tunneling effect).**Also, Read>>>** Healy Energy Frequency Device Review

At the heart of quantum physics are the mysterious probability amplitudes for all physical processes. Probability laws govern the values of physical quantities during a measurement. The probability amplitudes show interference, diffraction, and other phenomena like standing waves on vibrating strings or resonant cavities.

They lead to quantizing energy in many physical systems, starting with atoms and the electromagnetic field. However, they limit the interpretation of phenomena in terms of waves or classical particles. Heisenberg’s inequalities, for example, do not allow to attribute a velocity and a position to an electron simultaneously.

## Beneath the surface

Like the hydrogen atom here, an electron behaves neither like a ball nor like a wave on the water’s surface. Instead, it can be found on different atomic orbitals, described as probability densities of finding the electron at a point during an experiment.

These probability densities are derived from the quantum amplitudes governed by the Schrödinger equation. Some of these probability densities, which depend on integers, are represented in this diagram. They are more and more important when going from purple to yellow.

### From the atom to the stars, it’s always quantum physics

Trying to pin down the definition of quantum mechanics isn’t easy. First, there are the two worlds of the infinitely small (elementary particles) and the world of the infinitely large (the Big Bang and quantum cosmology). Second, quantum physics is in all fields of atomic, molecular, and of course, nuclear physics. There are, for example, quantum chemistry, quantum optics, and the physics of condensed matter.

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Thus, the laws of quantum mechanics explain why atoms and molecules are stable, emit and absorb light, and combine in chemical reactions. They explain phenomena as surprising as superconductivity and the superfluidity of helium and less exotic phenomena such as the ferromagnetism of magnets and the electrical conduction of metals or the existence of insulators. In addition, a whole zoo of new quantum excitations, called quasiparticles, is occasionally introduced in solid-state physics. The best known are phonons, magnons, and excitons.

## The sun and the moon

Quantum mechanics also explains why and how the Sun shines, with the synthesis reactions of helium and deuterium, and the origin of the carbon nuclei in our body. In addition, it allows us to understand the existence of white dwarfs and neutron stars and the composition of stars in galaxies, and the structure of the Milky Way via the study of spectral lines such as that of hydrogen at 21 cm.

### Quantum physics and technology

Quantum physics is finally at the heart of modern technology because the functioning of lasers, masers, CCDs, and the electronic components of our readers and computers are based on its laws. We can also mention the field of MRI and NMR-based techniques, as well as electron microscopy. Finally, the controlled fusion reactors that will succeed Iter in a few decades will use superconducting magnets like Iter.

It is also possible that a large-scale technological revolution is in the offing. Young disciplines of quantum information and mythical quantum computers are making this more of a reality. There is even speculation about the role that quantum mechanics could play in biology and neuroscience.

Another point to consider about our definition of Quantum mechanics: Quantum physics is not a finished field. In the early 1980’s they made significant moves to understand quantum physics. It’s not enough, however, considering that quantum physics has unexplored paradoxes. This includes both Schrödinger’s cat and the EPR effect.