ABSTRACT
The formalism for quantum systems developed so far applies to what are called pure states. A system in a pure state is completely specified by the state vector. A complete set of experimental tests will determine the system state fully: we have maximal knowledge of the system. For example, for a spin system, we can find a particular orientation of an SG machine such that the state is in its + or − port. This also means that the state is an eigenvector of some operator, or is always a linear combination of the computational basis states.
