Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Fermi-Hubbard Model block/interleaved inconsistency #1224

Open
ialsina opened this issue Aug 22, 2023 · 1 comment · May be fixed by #1245
Open

Fermi-Hubbard Model block/interleaved inconsistency #1224

ialsina opened this issue Aug 22, 2023 · 1 comment · May be fixed by #1245
Assignees
@ialsina
Labels
bug

Comments

@ialsina
Copy link

ialsina commented Aug 22, 2023

Environment

  • Qiskit Nature version: 343d290
  • Python version: 3.9.16
  • Operating system: RHEL 8.8

What is happening?

Since the introduction of InterleavedQubitMapper (#1046) the FermiHubbardModel class doesn't behave consistently with this feature, producing an interleaved-encoded hamiltonian when used together with JordanWignerMapper, and a block-encoded hamiltonian when used together with InterleavedQubitMapper.

How can we reproduce the issue?


>>> from qiskit_nature import settings
>>> from qiskit_nature.second_q.hamiltonians import FermiHubbardModel
>>> from qiskit_nature.second_q.hamiltonians.lattices import LineLattice
>>> from qiskit_nature.second_q.mappers import JordanWignerMapper, InterleavedQubitMapper
>>> settings.use_pauli_sum_op = False

>>> lattice = LineLattice(2)
>>> model = FermiHubbardModel(
    lattice.uniform_parameters(
        uniform_interaction=-1.,
        uniform_onsite_potential=0.
    ),
    onsite_interaction=1.
)
>>> hamiltonian = model.second_q_op().simplify()
>>> print(hamiltonian)

FermionicOp({'+_0 -_2': (-1+0j), '-_0 +_2': (1+0j), '+_1 -_3': (-1+0j), '-_1 +_3': (1+0j), '+_0 -_0 +_1 -_1': (1+0j), '+_2 -_2 +_3 -_3': (1+0j)}, num_spin_orbitals=4, )

>>> mapper = JordanWignerMapper()
>>> print(mapper.map(hamiltonian)) # Block encoding

SparsePauliOp(['IYZY', 'IXZX', 'YZYI', 'XZXI', 'IIII', 'IIZI', 'IIIZ', 'IIZZ', 'ZIII', 'IZII', 'ZZII'],
              coeffs=[-0.5 +0.j, -0.5 +0.j, -0.5 +0.j, -0.5 +0.j,  0.5 +0.j, -0.25+0.j,
 -0.25+0.j,  0.25+0.j, -0.25+0.j, -0.25+0.j,  0.25+0.j])

>>> interleaved_mapper = InterleavedQubitMapper(mapper)
>>> print(interleaved_mapper.map(hamiltonian)) # Interleaved encoding

SparsePauliOp(['IIYY', 'IIXX', 'YYII', 'XXII', 'IIII', 'IZII', 'IIIZ', 'IZIZ', 'ZIII', 'IIZI', 'ZIZI'],
              coeffs=[-0.5 +0.j, -0.5 +0.j, -0.5 +0.j, -0.5 +0.j,  0.5 +0.j, -0.25+0.j,
 -0.25+0.j,  0.25+0.j, -0.25+0.j, -0.25+0.j,  0.25+0.j])

What should happen?

For consistency with the other uses of JordanWignerMapper and InterleavedQubitMapper, the outcomes of the prints should be:

>>> hamiltonian = model.second_q_op().simplify()
>>> print(hamiltonian)

FermionicOp({'+_0 -_1': (-1+0j), '-_0 +_1': (1+0j), '+_2 -_3': (-1+0j), '-_2 +_3': (1+0j), '+_0 -_0 +_2 -_2': (1+0j), '+_1 -_1 +_3 -_3': (1+0j)}, num_spin_orbitals=4, )

>>> mapper = JordanWignerMapper()
>>> print(mapper.map(hamiltonian)) # Block encoding

SparsePauliOp(['IIYY', 'IIXX', 'YYII', 'XXII', 'IIII', 'IZII', 'IIIZ', 'IZIZ', 'ZIII', 'IIZI', 'ZIZI'],
              coeffs=[-0.5 +0.j, -0.5 +0.j, -0.5 +0.j, -0.5 +0.j,  0.5 +0.j, -0.25+0.j,
 -0.25+0.j,  0.25+0.j, -0.25+0.j, -0.25+0.j,  0.25+0.j])

>>> interleaved_mapper = InterleavedQubitMapper(mapper)
>>> print(interleaved_mapper.map(hamiltonian)) # Interleaved encoding

SparsePauliOp(['IYZY', 'IXZX', 'YZYI', 'XZXI', 'IIII', 'IIZI', 'IIIZ', 'IIZZ', 'ZIII', 'IZII', 'ZZII'],
              coeffs=[-0.5 +0.j, -0.5 +0.j, -0.5 +0.j, -0.5 +0.j,  0.5 +0.j, -0.25+0.j,
 -0.25+0.j,  0.25+0.j, -0.25+0.j, -0.25+0.j,  0.25+0.j])

Any suggestions?

In qiskit_nature/second_q/hamiltonians/fermi_hubbard_model.py, change the "index" variables everywhere from index = 2 * node + spin to index = node + spin * num_nodes. I am happy to open a PR with this change!
@ialsina ialsina added the bug label Aug 22, 2023
@mrossinek
Copy link
Member

I think unifying the behavior of the FermiHubbardModel with the block-ordering of the ElectronicEnergy class is a good idea! Please go ahead and open a PR as you had suggested 🙂

ialsina added a commit to ialsina/qiskit-nature that referenced this issue Sep 5, 2023
@ialsina
Unify orbital ordering of FermiHubbardModel with ElectronicEnergy (…
82f7361 
…qiskit-community#1224)
@ialsina ialsina linked a pull request Sep 5, 2023 that will close this issue
Open
@mrossinek mrossinek linked a pull request Sep 6, 2023 that will close this issue
Unify orbital ordering of FermiHubbardModel with ElectronicEnergy… #1245
Open
ialsina added a commit to ialsina/qiskit-nature that referenced this issue Nov 19, 2023
@ialsina
Unify orbital ordering of FermiHubbardModel with ElectronicEnergy (…
ecce6f8 
…qiskit-community#1224)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees

@ialsina ialsina

Labels
bug
Projects
None yet
Milestone
No milestone
Development

Successfully merging a pull request may close this issue.

Unify orbital ordering of FermiHubbardModel with ElectronicEnergy… ialsina/qiskit-nature
2 participants
@mrossinek @ialsina