add qiskit-symb as an optional dependency

README.md

@@ -123,12 +123,20 @@ To check the installation, open a python shell and type:
 import pyriemann_qiskit
 ```
 
-To enable Qiskit GPU optimization when using quantum simulation, run:
+To enable Qiskit GPU optimization (for Linux) when using quantum simulation, run:
+
+```
+pip install .[optim_linux]
+```
+
+To use symbolic quantum simulation, run:
 
 ```
 pip install .[optim]
 ```
 
+Which will enable [qiskit-symb](https://github.com/SimoneGasperini/qiskit-symb) integration.
+
 Note, Qiskit only provide binaries for Linux. For other platforms, or if you want to
 enable specific NVIDIA optimization for quantum, you need to build the binary
 [yourself](https://github.com/Qiskit/qiskit-aer/blob/main/CONTRIBUTING.md#building-with-gpu-support).

pyriemann_qiskit/classification.py

@@ -423,6 +423,7 @@ def _init_algo(self, n_features):
                 self.gen_feature_map,
                 self._quantum_instance,
                 self.use_fidelity_state_vector_kernel,
+                not self.pegasos
             )
             if self.pegasos:
                 self._log("[Warning] `gamma` is not supported by PegasosQSVC")

pyriemann_qiskit/utils/quantum_provider.py

@@ -15,7 +15,12 @@
     FidelityStatevectorKernel,
     FidelityQuantumKernel,
 )
-from qiskit_symb.quantum_info import Statevector
+try:
+    from qiskit_symb.quantum_info import Statevector
+    QISKIT_SYMB=True
+except:
+    QISKIT_SYMB=False
+
 
 
 class SymbFidelityStatevectorKernel:
@@ -209,14 +214,19 @@ def get_device(provider, min_qubits):
 
 
 def get_quantum_kernel(
-    feature_map, gen_feature_map, quantum_instance, use_fidelity_state_vector_kernel
+    feature_map,
+    gen_feature_map,
+    quantum_instance,
+    use_fidelity_state_vector_kernel,
+    use_qiskit_symb
 ):
     """Get a quantum kernel
 
     Return an instance of FidelityQuantumKernel or
     FidelityStatevectorKernel (in the case of a simulation).
 
-    For simulation with a small number of qubits (< 9), qiskit-symb is used.
+    For simulation with a small number of qubits (< 9), and `use_qiskit_symb` is True, 
+    qiskit-symb is used.
 
     Parameters
     ----------
@@ -225,7 +235,10 @@ def get_quantum_kernel(
     quantum_instance: BaseSampler
         A instance of BaseSampler.
     use_fidelity_state_vector_kernel: boolean
-        if True, use a FidelitystatevectorKernel for simulation.
+        If True, use a FidelitystatevectorKernel for simulation.
+    use_qiskit_symb: boolean
+        This flag is used only if qiskit-symb is installed.
+        If True and the number of qubits < 9, then qiskit_symb is used.
 
     Returns
     -------
@@ -242,7 +255,7 @@ def get_quantum_kernel(
         quantum_instance._backend, AerSimulator
     ):
         # For simulation:
-        if feature_map.num_qubits <= 9:
+        if QISKIT_SYMB and feature_map.num_qubits <= 9 and use_qiskit_symb:
             # With a small number of qubits, let's use qiskit-symb
             # See:
             # https://medium.com/qiskit/qiskit-symb-a-qiskit-ecosystem-package-for-symbolic-quantum-computation-b6b4407fa705

requirements.txt

@@ -14,4 +14,4 @@ docplex>=2.21.207
 firebase_admin==6.5.0
 tqdm
 pandas
-qiskit-symb
+

setup.py

@@ -50,7 +50,6 @@
                         'scikit-learn==1.5.1',
                         'tqdm',
                         'pandas',
-                        'qiskit-symb'
                         ],
       extras_require={'docs': [
                                 'sphinx-gallery',
@@ -65,6 +64,7 @@
                       'tests': ['pytest', 'seaborn', 'flake8', 'mne', 'pooch'],
                       # GPU optimization not available on all platform.
                       # See https://github.com/Qiskit/qiskit-aer/issues/929#issuecomment-691716936
-                      'optim': ['qiskit-aer-gpu==0.15.0']},
+                      'optim': ['qiskit-symb'],
+                      'optim_linux': ['qiskit-aer-gpu==0.15.0']},
       zip_safe=False,
 )