マップ演算子の表現

>>> from qiskit.quantum_info import SparseObservable
>>> from qiskit_fermions.mappers import map_majorana_action_generators
>>> from qiskit_fermions.operators import MajoranaOperator
>>>
>>> # Create a Majorana operator
>>> maj_op = MajoranaOperator.from_dict({(0, 1): 1.0, (2,): 0.5})
>>>
>>> # Define how each Majorana action maps to Pauli strings
>>> num_qubits = 2
>>> def map_action(mode: int) -> SparseObservable:
...     idx = mode // 2
...     qubits = list(range(idx + 1))
...     pauli = "Y" if mode % 2 else "X"
...     return SparseObservable.from_sparse_list(
...         [("Z" * idx + pauli, qubits, 1.0)],
...         num_qubits=num_qubits,
...     )
>>>
>>> # Apply the mapping to transform the operator
>>> custom_observable = map_majorana_action_generators(
...     maj_op,
...     map_action,
...     identity=lambda: SparseObservable.identity(num_qubits),
...     compose=SparseObservable.compose,
... )
>>> print(custom_observable.simplify())
<SparseObservable with 2 terms on 2 qubits: (0+1j)(Z_0) + (0.5+0j)(X_1 Z_0)>

// The C API provides direct mapping functions for common transformations.
// Custom mapper prototyping as shown in Python is primarily a Python feature.
// For custom mappings in C, you will need to perform the iteration and
// conversion logic entirely by yourself.

>>> from qiskit_fermions.mappers.library import majorana_to_fermion, jordan_wigner
>>>
>>> # Convert MajoranaOperator to FermionOperator using library mapper
>>> ferm_op = majorana_to_fermion(maj_op)
>>>
>>> # Apply Jordan-Wigner mapper to get qubit operator
>>> sparse_observable = jordan_wigner(ferm_op, num_qubits=2)
>>> difference = sparse_observable - custom_observable
>>> print(difference.simplify() == SparseObservable.zero(num_qubits))
True

#include <qiskit_fermions.h>

// Create a MajoranaOperator with the same terms as maj_op above
uint64_t num_terms = 2;
uint64_t num_modes = 3;
uint32_t modes[3] = {0, 1, 2};
QkComplex64 coeffs[2] = {{1.0, 0.0}, {0.5, 0.0}};
uint32_t boundaries[3] = {0, 2, 3};
QfMajoranaOperator *maj_op = qf_maj_op_new(num_terms, num_modes, coeffs, modes, boundaries);

// Convert MajoranaOperator to FermionOperator using library mapper
QfFermionOperator *ferm_op = qf_majorana_to_fermion(maj_op);

// Apply Jordan-Wigner mapper to get qubit operator
QkObs *qubit_op;
QfExitCode exit = qf_ferm_op_jordan_wigner(ferm_op, 2, &qubit_op);
assert(exit == QfExitCode_Success);

// Clean up
qf_ferm_op_free(ferm_op);
qf_maj_op_free(maj_op);
qk_obs_free(qubit_op);