Figure 1

The general${\mathit{K}}_{\mathit{a}}^{\mathit{j}}$ancilla-register interaction. (a) Decomposition into local and non-local parts. (b) In this minimal control model the elements of a universal set for single-qubit unitaries, $\{u_0,u_1\}$, are applied to the register by the $K_a^j$ interaction and initialising the ancilla in the state $|i〉$ where $i=0,1$.