Answer

Quantum physics is an ab initio model because its predictions such as the electronic structure of molecules or material properties, are calculated directly from fundamental axioms like the Schrödinger or Dirac equations using only universal physical constants (e.g., Planck’s constant, electron mass, and charge)
Classical mechanics is also considered ab initio because the complex dynamics of physical systems are mathematically deduced from a strict set of fundamental axioms like Newton’s Laws of Motion (or equivalently, Hamilton’s equations and the Principle of Least Action).