qft.hpp

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#ifndef QNLP_QFT
#define QNLP_QFT

#include <cmath>

namespace QNLP{
    template <class SimulatorType>
    class QFT{
        public:
        static void applyQFT(SimulatorType& qSim, const unsigned int minIdx, const unsigned int maxIdx){
            double theta=0;

            //target lines
            for(int i = maxIdx; i >= (int) minIdx; i--){
                qSim.applyGateH(i);

                //Control lines:
                for(int j = i-1; j >= (int) minIdx; j--){
                    theta = 2.0*M_PI / (std::size_t) (0b1<<(1+(i-j)));
                    qSim.applyGateCPhaseShift(theta, j,  i);
                }
            }
            qSim.InvertRegister(minIdx, maxIdx);
        }

        static void applyIQFT(SimulatorType& qSim, const unsigned int minIdx, const unsigned int maxIdx){
            double theta=0;
            qSim.InvertRegister(minIdx, maxIdx);

            //Target lines
            for(int i = minIdx; i <= (int) maxIdx; i++){

                //Control lines:
                for(int j = minIdx; j < i; j++){
                    theta = -2.0*M_PI / (std::size_t) (0b1<<(1+(i-j)));
                    qSim.applyGateCPhaseShift(theta, j,  i);
                }
                qSim.applyGateH( i );
            }
        }
    };
}
#endif