Quantum superposition

Summary

Quantum superposition is the principle that a normalised linear combination of state vectors of a quantum system is again a state vector of the system. It holds because pure quantum states are rays in a complex Hilbert space, a vector space. The relative phases of the coefficients matter and produce interference, while an overall phase does not. It is the quantum form of the superposition principle for linear equations, here the linear Schrödinger equation.