apply_unitary

auto syten::T3N::BasisTransformation::apply_unitary

Initial value:

= [](STensor const& t1t2, 
                              STensor const& transformer, 
                              SBasis const& merged_basis,
                              SBasis const& p1, 
                              SBasis const& p2) {
        
        auto [q, r, qr_basis] = qr(transformer, 
                                   merged_basis);
        q = project(std::move(q), 
                    qr_basis, 
                    merged_basis);
        return demerge((t1t2 * q).unprime(merged_basis),
                       p1,p2);
      }