The term “quantum” is commonly used in the context of quantum physics, also known as quantum mechanics, which is a branch of physics that deals with phenomena on a very small scale, such as molecules, atoms, and subatomic particles like electrons, protons, and photons.
The word “quantum” itself comes from the Latin “quantus,” meaning “how much.” In quantum mechanics, it refers to the discrete units in which certain physical quantities may occur. For example, energy in an atom does not vary continuously but exists in discrete levels. That is, there is a “smallest” possible unit of energy, and changes in energy are always multiples of this unit, never a fraction. This is quite different from classical mechanics, where quantities are usually continuous and can take on any value.
Image by Gerd Altmann from Pixabay
Key principles and phenomena associated with quantum mechanics include wave-particle duality (the idea that every particle also has aspects of a wave), uncertainty principle (the concept that the position and momentum of a particle cannot both be precisely measured at the same time), quantum entanglement (a phenomenon where particles become interconnected and the state of one can instantly affect the state of the other, regardless of the distance between them), and superposition (the concept that a particle can exist in multiple states at once, and only upon measurement does the particle “collapse” into one state).
Quantum mechanics is known for being counterintuitive and differing drastically from the rules we observe in the macroscopic world. However, it has been extensively tested and is currently the most accurate description of the natural world at very small scales. It has led to the development of many modern technologies, such as lasers, semiconductors, and magnetic resonance imaging (MRI), and is the foundational theory for the emerging field of quantum computing.
