# Import
from qiskit_nature.second_q.hamiltonians.lattices import BoundaryCondition, SquareLattice
from qiskit_nature.second_q.mappers import JordanWignerMapper
from qiskit_nature.second_q.hamiltonians import FermiHubbardModel

from qiskit.synthesis import LieTrotter, SuzukiTrotter
from qiskit.circuit.library import PauliEvolutionGate

from qiskit.circuit import Parameter
from qiskit.quantum_info import SparsePauliOp


# Prepare Hamiltonian
jw_mapper = JordanWignerMapper()
PERIODIC = BoundaryCondition.PERIODIC

rows = 2
cols = 2
square_lattice = SquareLattice(rows=rows, cols=cols, boundary_condition = PERIODIC)

t = -1  # the interaction parameter
v =  3 # the onsite potential
u = 7  # the interaction parameter u

fhm = FermiHubbardModel(
    lattice = square_lattice.uniform_parameters(uniform_interaction = t, uniform_onsite_potential = v),
    onsite_interaction = u
)
fhm_sq = fhm.second_q_op().simplify()
groups = jw_mapper.map(fhm_sq).group_commuting(qubit_wise= True) 
fhm_ham = sum(groups)                                                   # With Grouping
# fhm_ham = jw_mapper.map(fhm_sq)                                       # Without Grouping

# test_ham = SparsePauliOp(['XXXX', 'YYYY', 'ZZII','ZZZZ'],[2,3,5,7])      # Expected output is available through this 

# Prepare Ansatz
t = Parameter('t')
# t = 1.2
time_evolution_operator = PauliEvolutionGate(fhm_ham, time=t)
# time_evolution_operator = PauliEvolutionGate(test_ham, time=t)      # Expected output is available through this 


# lie_trotter_factory = LieTrotter(reps=1, insert_barriers=True, wrap = True, preserve_order= True)
# evolution_circuit = lie_trotter_factory.synthesize(time_evolution_operator)    

suzuki_trotter_factory = SuzukiTrotter(order=2, reps=1, insert_barriers=True, wrap = True, preserve_order= True)
evolution_circuit = suzuki_trotter_factory.synthesize(time_evolution_operator)

# Draw Circuit
evolution_circuit.decompose(reps = 1).draw(fold = -1)

thread '<unnamed>' panicked at crates[/circuit/src/operations.rs:2353:14](http://localhost:8888/circuit/src/operations.rs#line=2352):
internal error: entered unreachable code
---------------------------------------------------------------------------
PanicException                            Traceback (most recent call last)
Cell In[19], line 47
     40 # time_evolution_operator = PauliEvolutionGate(test_ham, time=t)
     41 
     42 
     43 # lie_trotter_factory = LieTrotter(reps=1, insert_barriers=False, wrap = True, preserve_order= True)
     44 # evolution_circuit = lie_trotter_factory.synthesize(time_evolution_operator)
     46 suzuki_trotter_factory = SuzukiTrotter(order=2, reps=1, insert_barriers=False, wrap = True, preserve_order= True)
---> 47 evolution_circuit = suzuki_trotter_factory.synthesize(time_evolution_operator)

File [~/.local/lib/python3.12/site-packages/qiskit/synthesis/evolution/product_formula.py:161](http://localhost:8888/lab/tree/qc-research/New%20Tests/HVA/~/.local/lib/python3.12/site-packages/qiskit/synthesis/evolution/product_formula.py#line=160), in ProductFormula.synthesize(self, evolution)
    156 num_qubits = evolution.num_qubits
    158 if self._wrap or self._atomic_evolution is not None:
    159     # this is the slow path, where each Pauli evolution is constructed in Rust
    160     # separately and then wrapped into a gate object
--> 161     circuit = self._custom_evolution(num_qubits, pauli_rotations)
    162 else:
    163     # this is the fast path, where the whole evolution is constructed Rust-side
    164     cx_fountain = self._cx_structure == "fountain"

File [~/.local/lib/python3.12/site-packages/qiskit/synthesis/evolution/product_formula.py:223](http://localhost:8888/lab/tree/qc-research/New%20Tests/HVA/~/.local/lib/python3.12/site-packages/qiskit/synthesis/evolution/product_formula.py#line=222), in ProductFormula._custom_evolution(self, num_qubits, pauli_rotations)
    220 local_pauli = (pauli_string, list(range(len(qubits))), coeff)
    222 # build the circuit Rust-side
--> 223 data = pauli_evolution(
    224     len(qubits),
    225     [local_pauli],
    226     False,
    227     cx_fountain,
    228 )
    229 evo = QuantumCircuit._from_circuit_data(data)
    231 # and append it to the circuit with the correct label

PanicException: internal error: entered unreachable code