Editing Quantum superposition (section)

== Wave postulate ==
The theory of quantum mechanics postulates that a [[wave equation]] completely determines the state of a quantum system at all times. Furthermore, this differential equation is restricted to be [[linear differential equation|linear]] and [[homogeneous differential equation|homogeneous]]. These conditions mean that for any two solutions of the wave equation, <math>\Psi_1</math> and <math>\Psi_2</math>, a linear combination of those solutions also solve the wave equation:
<math display="block">\Psi = c_1\Psi_1 + c_2\Psi_2</math>
for arbitrary complex coefficients <math>c_1</math> and <math>c_2</math>.<ref name=Messiah>{{Cite book |last=Messiah |first=Albert |title=Quantum mechanics. 1 |date=1976 |publisher=North-Holland |isbn=978-0-471-59766-7 |edition=2|location=Amsterdam}}</ref>{{rp|61}} If the wave equation has more than two solutions, combinations of all such solutions are again valid solutions.