TwoSiteGate.h

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#ifndef TWO_SITE_GATE_H_
#define TWO_SITE_GATE_H_
 
#include "tensors/Qbasis.h"
 
template<typename Symmetry, typename Scalar>
class TwoSiteGate
{
public:
    TwoSiteGate() {};
    TwoSiteGate(const vector<vector<vector<vector<vector<Scalar> > > > > &data_in) : data(data_in){};
    TwoSiteGate(const Qbasis<Symmetry> &s1, const Qbasis<Symmetry> &s2);
 
    void print() const;
 
    //
    //        s1p  s2p
    //         |    |
    //  swap=  ****** = delta(s1,s2p)*delta(s2,s1p)
    //         |    |
    //        s1   s2
    //
    void setSwapGate(bool FERMIONIC=false);
 
    void setIdentity();
    
    Qbasis<Symmetry> midBasis() const {return Bmid;}
    Qbasis<Symmetry> leftBasis() const {return B1;}
    Qbasis<Symmetry> rightBasis() const {return B2;}
    
//private:
    //data[s1][s2][s1_p][s2_p][k]:
    //
    //   s1p  s2p          s1p  s2p
    //    |    |            \   /
    //    ^    ^             \ /
    //    |    |              ^
    //    ******              |
    //    *gate*     CGC:     k
    //    ******              ^
    //    |    |              |
    //    ^    ^             / \
    //    |    |            /   \
    //   s1   s2          s1     s2
    //
    vector<vector<vector<vector<vector<Scalar> > > > > data;
    Qbasis<Symmetry> B1, B2, Bmid;
 
    vector<qarray<Symmetry::Nq> > qloc1, qloc2, qmid;
    
    void resize();
};
 
template<typename Symmetry, typename Scalar>
TwoSiteGate<Symmetry,Scalar>::
TwoSiteGate (const Qbasis<Symmetry> &s1, const Qbasis<Symmetry> &s2)
    : B1(s1),B2(s2)
{
    //Bmid is the combined basis from B1 and B2.
    Bmid = B1.combine(B2);
    qloc1 = B1.qloc();
    qloc2 = B2.qloc();
    qmid = Bmid.qs();
    resize();
}
 
template<typename Symmetry, typename Scalar>
void TwoSiteGate<Symmetry,Scalar>::
resize()
{
    data.resize(qloc1.size());
    for (size_t s1=0; s1< qloc1.size(); s1++)
    {
        data[s1].resize(qloc2.size());
        for (size_t s2=0; s2<qloc2.size(); s2++)
        {
            data[s1][s2].resize(qloc1.size());
            for (size_t s1p=0; s1p<qloc1.size(); s1p++)
            {
                data[s1][s2][s1p].resize(qloc2.size());
                for (size_t s2p=0; s2p<qloc2.size(); s2p++)
                {
                    data[s1][s2][s1p][s2p].resize(qmid.size());
                }
            }
        }
    }
}
 
 
template<typename Symmetry, typename Scalar>
void TwoSiteGate<Symmetry,Scalar>::
setSwapGate(bool FERMIONIC)
{
    assert(!FERMIONIC and "Fermionic swap gates are not yet implemented.");
    for (size_t s1=0;  s1<qloc1.size();  s1++)
    for (size_t s2=0;  s2<qloc2.size();  s2++)
    for (size_t s1p=0; s1p<qloc1.size(); s1p++)
    for (size_t s2p=0; s2p<qloc2.size(); s2p++)
    for (size_t k=0;    k<qmid.size();   k++)
    {
        if (!Symmetry::triangle({qloc1[s1],qloc2[s2],qmid[k]})) {continue;}
        if (!Symmetry::triangle({qloc1[s1p],qloc2[s2p],qmid[k]})) {continue;}
        if (s1 == s2p and s2 == s1p)
        {
            // cout << "s1=" << s1 << "," << qloc1[s1] << ", s2p=" << s2p << "," << qloc2[s2p] << ", s2=" << s2 << "," << qloc2[s2] << ", s1p=" << s1p << "," << qloc1[s1p] << ", k=" << k << "," << qmid[k] << endl;
            // cout << "CGC phase=" << Symmetry::coeff_swapPhase(qloc1[s1],qloc2[s2],qmid[k]) << endl;
            data[s1][s2][s1p][s2p][k] = Symmetry::coeff_swapPhase(qloc1[s1],qloc2[s2],qmid[k])*Scalar(1.);
        }
        else {data[s1][s2][s1p][s2p][k] = Scalar(0.);}
    }
}
 
template<typename Symmetry, typename Scalar>
void TwoSiteGate<Symmetry,Scalar>::
setIdentity()
{
    for (size_t s1=0;  s1<qloc1.size();  s1++)
    for (size_t s2=0;  s2<qloc2.size();  s2++)
    for (size_t s1p=0; s1p<qloc1.size(); s1p++)
    for (size_t s2p=0; s2p<qloc2.size(); s2p++)
    for (size_t k=0;    k<qmid.size();   k++)
    {
        if (s1 == s1p and s2 == s2p)
        {
            data[s1][s2][s1p][s2p][k] = Scalar(1.);
        }
        else {data[s1][s2][s1p][s2p][k] = Scalar(0.);}
    }
}
 
template<typename Symmetry, typename Scalar>
void TwoSiteGate<Symmetry,Scalar>::
print() const
{
    for (size_t s1=0;  s1<qloc1.size();  s1++)
    for (size_t s2=0;  s2<qloc2.size();  s2++)
    for (size_t s1p=0; s1p<qloc1.size(); s1p++)
    for (size_t s2p=0; s2p<qloc2.size(); s2p++)
    for (size_t k=0;    k<qmid.size();   k++)
    {
        cout << "data[" << s1 << "][" << s2 << "][" << s1p << "][" << s2p << "][" << k << "]=" << data[s1][s2][s1p][s2p][k] << endl; 
    }
}
 
 
#endif