Quantum superposition is the fundamental law of quantum mechanics. It defines the allowed state space of a quantum mechanical system.

Superposition Principle

The principle of superposition states that if the world can be in any configuration, any possible arrangement of particles or fields, and if the world could also be in another configuration, then the world can also be in a state which is a mixture of the two, where the amount of each configuration that is in the mixture is specified by a complex number.