Its all about Physics.

  Quantum Physics: Introduction: The physical features of nature at the size of atoms and subatomic particles are described by the fundamental physics theory known as quantum mechanics. It serves as the theoretical cornerstone for all branches of quantum physics, including quantum information science, quantum technology, quantum field theory, and quantum chemistry.   Quantum Physics Many parts of nature are described by classical physics, a body of theories that predated the development of quantum mechanics, at a large (macroscopic) scale, but not well enough at microscopic (atomic and subatomic) sizes. The majority of classical physics theories can be derived from quantum mechanics as a large-scale (macroscopic) approximation.   With regard to energy, momentum, angular momentum, and other quantities of a bound system, quantum mechanics differs from classical physics in that these quantities are constrained to discrete values (quantization); objects have characteristics o...