### Problems with add_local_term and H.c

Posted:

**01 Feb 2022, 19:42**Hi,

I'm trying to decrease the number of terms appearing in the Hamiltonian MPO by using H. c. in add_coupling_term. However, when I use plus_hc I always get an error. I have tried this with different models, and I get the same error. I provide an example below.

I have a ladder of SpinHalfFermions on a Chain lattice with the following hopping coupling terms:

self.add_local_term(-adj_mat[i, j], [('Cdu', (i, 0)), ('Cu', (j, 0))])

self.add_local_term(adj_mat[i, j], [('Cu', (i, 0)), ('Cdu', (j, 0))])

self.add_local_term(-adj_mat[i, j], [('Cdd', (i, 0)), ('Cd', (j, 0))])

self.add_local_term(adj_mat[i, j], [('Cd', (i, 0)), ('Cdd', (j, 0))])

This case works without any problem. However, when I change to:

self.add_local_term(-adj_mat[i, j], [('Cdu', (i, 0)), ('Cu', (j, 0))],plus_hc=True)

self.add_local_term(adj_mat[i, j], [('Cd', (i, 0)), ('Cdd', (j, 0))],plus_hc=True)

I receive the error:

IndexError: tuple index out of range

Am I doing something wrong?

F. P. M. MÃ©ndez-Cordoba.

I'm trying to decrease the number of terms appearing in the Hamiltonian MPO by using H. c. in add_coupling_term. However, when I use plus_hc I always get an error. I have tried this with different models, and I get the same error. I provide an example below.

I have a ladder of SpinHalfFermions on a Chain lattice with the following hopping coupling terms:

self.add_local_term(-adj_mat[i, j], [('Cdu', (i, 0)), ('Cu', (j, 0))])

self.add_local_term(adj_mat[i, j], [('Cu', (i, 0)), ('Cdu', (j, 0))])

self.add_local_term(-adj_mat[i, j], [('Cdd', (i, 0)), ('Cd', (j, 0))])

self.add_local_term(adj_mat[i, j], [('Cd', (i, 0)), ('Cdd', (j, 0))])

This case works without any problem. However, when I change to:

self.add_local_term(-adj_mat[i, j], [('Cdu', (i, 0)), ('Cu', (j, 0))],plus_hc=True)

self.add_local_term(adj_mat[i, j], [('Cd', (i, 0)), ('Cdd', (j, 0))],plus_hc=True)

I receive the error:

IndexError: tuple index out of range

Am I doing something wrong?

F. P. M. MÃ©ndez-Cordoba.