A Complete Equational Theory for Quantum Circuits

We introduce the first complete equational theory for quantum circuits. More precisely, we introduce a set of circuit equations that we prove to be sound and complete: two circuits represent the same unitary map if and only if they can be transformed one into the other using the equations. The proof is based on the properties of multi-controlled gates -that are defined using elementary gates -together with an encoding of quantum circuits into linear optical circuits, which have been proved to have a complete axiomatisation.

2 Raw terms are for instance similarly used [31] as an intermediate step in the defintion of prop. 3 denotes the identity, the swap and the empty circuit. 4 We use the standard Dirac notations.