Earlier we said that the projection of the state vector onto one of the perpendicular axes of its Hilbert Space shows the contribution of that axes' eigenstate to the whole state. According to quantum physics a quantum system can exist in a mix of all of its allowed states simultaneously. This is the Principle of Superposition, and it is key to the power of the quantum computer. While the physics of superposition is not simple at all, mathematically it is not difficult to characterize this kind of behavior.