The Carry and Sum Networks by Vedral et.al

The following figure and it's caption is taken from quant-ph/9511018 (Vedral et.al.: Quantum networks for elementary arithmetic operations).

Basic carry and sum operations for the plain addition network. i) the carry operation (note that the carry operation perturbs the state of the qubit b). ii) the sum operation.

void EqcsVedral::carry(EqcsGateArray &a, int b0, int b1, int b2, int b3)
{
    a.push_back(CCNot(b0, b1, b2));
    a.push_back(CNot(b1, b2));
    a.push_back(CCNot(b0, b1, b3));
}

void EqcsVedral::rcarry(EqcsGateArray &a, int b0, int b1, int b2, int b3)
{
    a.push_back(CCNot(b0, b1, b3));
    a.push_back(CNot(b1, b2));
    a.push_back(CCNot(b0, b1, b2));
}

void EqcsVedral::sum(EqcsGateArray &a, int b0, int b1, int b2)
{
    a.push_back(CNot(b0, b1));
    a.push_back(CNot(b0, b2));
}

void EqcsVedral::rsum(EqcsGateArray &a, int b0, int b1, int b2)
{
    a.push_back(CNot(b0, b2));
    a.push_back(CNot(b0, b1));
}