Function localiser_statevec_multiQubitProjector

quest/src/core/localiser.cpp:2321–2339

void localiser_statevec_multiQubitProjector(Qureg qureg, vector<int> qubits, vector<int> outcomes, qreal prob) {

    // this routine is always embarrassingly parallel; however, we handle the
    // prefix-qubits here so that the backend can receive only the suffix qubits
    // and ergo be agnostic to distribution (so that we can e.g. use cuQuantum).
    // any rank which has a prefix-qubit inconsistent with outcomes is zero'd

    // nodes with all basis states orthogonal to outcomes (because prefix differs) are zero'd
    if (!doAnyLocalStatesHaveQubitValues(qureg, qubits, outcomes)) {
        accel_statevec_initUniformState_sub(qureg, 0);
        return;
    }

    // all other nodes has some or all states consistent with suffix outcomes
    removePrefixQubitsAndStates(qureg, qubits, outcomes);
    (qubits.empty())?
        localiser_statevec_scaleAmps(qureg, 1/std::sqrt(prob)):
        accel_statevec_multiQubitProjector_sub(qureg, qubits, outcomes, prob);
}


void localiser_densmatr_multiQubitProjector(Qureg qureg, vector<int> qubits, vector<int> outcomes, qreal prob) {