mps-0.0.0
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sparse_hamiltonian.cc
1 // -*- mode: c++; fill-column: 80; c-basic-offset: 2; indent-tabs-mode: nil -*-
2 /*
3  Copyright (c) 2010 Juan Jose Garcia Ripoll
4 
5  Tensor is free software; you can redistribute it and/or modify it
6  under the terms of the GNU Library General Public License as published
7  by the Free Software Foundation; either version 2 of the License, or
8  (at your option) any later version.
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10  This program is distributed in the hope that it will be useful,
11  but WITHOUT ANY WARRANTY; without even the implied warranty of
12  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13  GNU Library General Public License for more details.
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15  You should have received a copy of the GNU General Public License along
16  with this program; if not, write to the Free Software Foundation, Inc.,
17  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
18 */
19 
20 #include <mps/quantum.h>
21 #include <mps/hamiltonian.h>
22 
23 namespace mps {
24 
25  const CSparse
26  sparse_hamiltonian(const Hamiltonian &H, const double t)
27  {
28  index N = H.size();
29  bool periodic = H.is_periodic();
30  std::vector<CSparse> H12(N);
31  std::vector<CSparse> H1(N);
32  for (index k = 0; k < N; k++) {
33  H1.at(k) = CSparse(H.local_term(k, t));
34  if ((k < (N-1)) || periodic)
35  if (H.interaction_depth(k))
36  H12.at(k) = CSparse(H.interaction(k, t));
37  }
38  return sparse_1d_hamiltonian(H12, H1, periodic);
39  }
40 
41 } // namespace mps
const CSparse sparse_hamiltonian(const Hamiltonian &H, double t=0.0)
Create a sparse matrix using the information in Hamiltonian.
virtual const CTensor interaction(index k, double t=0.0) const =0
Nearest neighbor interaction between sites 'k' and 'k+1'.
virtual bool is_periodic() const =0
Is there interaction between the first and the last sites?
virtual const CTensor local_term(index k, double t=0.0) const =0
Local term of the Hamiltonian on site 'k'.
const CSparse sparse_1d_hamiltonian(const CSparse &H12, const CSparse &Hlocal, index size, bool periodic=false)
Create the Hamiltonian of a translationary invariant model.
Base class for 1D lattice Hamiltonians.
Definition: hamiltonian.h:33