

Figure 1.
Quantum circuit representation of the swap test.

Figure 2.
Representation of the construction of the circuit C1 ⊕p C2 from the circuits C1 and C2 in canonical form, with out(C2) < out(C1). Up is a unitary that implements the map to good approximation.

Figure A1.
Construction of the channel from a QMA(2)-language verification circuit.