The term “ab initio” in quantum physics refers to a theory derived from first principles rather than derived from empirical data or a model that is constructed to fit observations. Physical systems are predicted using basic principles, such as the Schrödinger equation. Classical mechanics consider Newton’s laws of motion as their first principles, so they can be used to predict physical systems’ behaviour without relying on empirical data. Accordingly, classical electromagnetism is based on Maxwell’s equation, which describes the interaction between charged particles and electric fields. It predicts electric and magnetic fields in a variety of physical systems.