Quantum Physics

Quantum Mechanics is the fundamental theory in physics that provides the mathematical framework for describing the behavior of nature at the scale of atoms and subatomic particles. As the foundation of all quantum physics, it departs from classical mechanics by introducing concepts such as quantization, where physical properties exist in discrete units; wave-particle duality, the principle that particles can exhibit both wave and particle characteristics; and the uncertainty principle, which sets a fundamental limit on the precision with which pairs of properties like position and momentum can be known. The theory is inherently probabilistic, using the Schrödinger equation to calculate the likelihood of an outcome rather than a deterministic result.

Quantum Field Theory (QFT) is the theoretical framework that merges the principles of quantum mechanics with Einstein's special relativity, providing the foundation for the Standard Model of particle physics. It posits that the fundamental entities of the universe are not particles but continuous fields that permeate all of spacetime. Particles, such as electrons and photons, are understood as localized excitations or "quanta" of these fields, and their interactions, creations, and annihilations are described by the dynamics of these underlying fields, successfully explaining the electromagnetic, weak, and strong nuclear forces.

Quantum Optics is a subfield of physics that applies the principles of quantum mechanics to study the fundamental nature of light and its interaction with matter. Moving beyond the classical wave description, this field treats light as being composed of discrete, quantized particles called photons, allowing for the investigation of phenomena that have no classical counterpart, such as quantum entanglement, superposition, and the particle-like behavior of individual photons. The principles of quantum optics are foundational to the operation of lasers and are driving the development of next-generation technologies including quantum computing, quantum cryptography, and ultra-precise sensors.

Atomic and Molecular Physics is the branch of quantum physics that studies the structure and properties of atoms and simple molecules. It focuses on the arrangement of electrons and atomic nuclei and the processes by which these arrangements change, such as through interactions with each other or with electromagnetic radiation (light). This field provides the fundamental understanding of quantized energy levels, chemical bonding, and the absorption and emission of photons, which underpins modern spectroscopy, laser physics, and quantum chemistry.