A Simplified Stabilizer ZX-calculus
The stabilizer ZX-calculus is a rigorous graphical language for reasoning about stabilizer quantum mechanics. This language has been proved to be complete in two steps: first in a setting where scalars (diagrams with no inputs or outputs) are ignored and then in a more general setting where a new symbol and three additional rules have been added to keep track of scalars. Here, we introduce a simplified version of the stabilizer ZX-calculus: we give a smaller set of axioms and prove that meta-rules like `only the topology matters', `colour symmetry' and `upside-down symmetry', which were considered as axioms in previous versions of the stabilizer ZX-calculus, can in fact be derived. In particular, we show that the additional symbol and one of the rules introduced for proving the completeness of the scalar stabilizer ZX-calculus are not necessary. We furthermore show that the remaining two rules dedicated to scalars cannot be derived from the other rules, i.e. they are necessary.