Function anyCtrlZTensorOrGadget

quest/src/core/localiser.cpp:1261–1282

void anyCtrlZTensorOrGadget(Qureg qureg, vector<int> ctrls, vector<int> ctrlStates, vector<int> targs, bool isGadget, qcomp phase) {     
    assertValidCtrlStates(ctrls, ctrlStates);
    setDefaultCtrlStates(ctrls, ctrlStates);

    // node has nothing to do if all local amps violate control condition
    if (!doAnyLocalStatesHaveQubitValues(qureg, ctrls, ctrlStates))
        return;

    // retain only suffix control qubits, as relevant to local amp modification
    removePrefixQubitsAndStates(qureg, ctrls, ctrlStates);

    // prefixZ merely applies a node-wide factor to fac0 and fac1
    auto [prefixZ, suffixZ] = util_getPrefixAndSuffixQubits(targs, qureg);
    int sign = paulis_getPrefixZSign(qureg, prefixZ);
    
    // tensor multiplies +-1, gadget multiplies exp(+- i phase)
    qcomp fac0 = (isGadget)? std::exp(+ phase * sign * 1_i) : +1 * sign;
    qcomp fac1 = (isGadget)? std::exp(- phase * sign * 1_i) : -1 * sign;

    // simulation is always embarrassingly parallel
    accel_statevector_anyCtrlAnyTargZOrPhaseGadget_sub(qureg, ctrls, ctrlStates, suffixZ, fac0, fac1);
}


void anyCtrlPauliTensorOrGadget(Qureg qureg, vector<int> ctrls, vector<int> ctrlStates, PauliStr str, qcomp ampFac, qcomp pairAmpFac) {