All quantum systems can be described by a linear combination of basis states. Basis states describe the possible outcome states of measurements. For example, a qubit is described by a point on the Bloch Sphere, written as c0|0⟩+c1|1⟩. The complex numbers c0, c1 determine the probabilities |c0|2, |c1|2 of measuring the qubit in either the |0⟩ or |1⟩ state of a particular measurement (Z-measurement in this example), respectively. When a quantum system is written as such a sum, we say it is in a superposition of the outcome states.