On page 11 of this study they write that "In order to calculate macroscopic values according to Eq.(11), point-wise addition of the distribution function ... is required. To perform this operation quantumly, a quantum circuit composed of controlled H, SWAP, and X gate is applied ... while an addition procedure is conducted by applying the Hadamard operation." They then go on to give an explicit circuit to do this operation (Fig. 7).
My question is, what do they mean by "point-wise addition?" Is this the same as using an adder function as discussed here? If not, what are they doing differently? It seems to me like they may be adding probability amplitudes, but that doesn't seem possible since I don't think it is a unitary operation.