function

src/qibo/quantum_info/clifford.py

@@ -140,7 +140,9 @@ def generators(self, return_array: bool = False):
             self.symplectic_matrix, return_array
         )
 
-    def stabilizers(self, symplectic: bool = False, return_array: bool = False):
+    def stabilizers(
+        self, symplectic: bool = False, return_array: bool = False, cores: int = 1
+    ):
         """Extracts the stabilizers of the state.
 
         Args:
@@ -150,6 +152,8 @@ def stabilizers(self, symplectic: bool = False, return_array: bool = False):
             return_array (bool, optional): To be used when ``symplectic = False``.
                 If ``True`` returns the stabilizers as ``ndarray``.
                 If ``False``, returns stabilizers as strings. Defaults to ``False``.
+            cores (int, optional): number of processes to be used to calculate all stabilizers.
+                To be used ``symplectic=False`` and ``return_array=False``. Defaults to :math:`1`.
 
         Returns:
             (ndarray or list): Stabilizers of the state.
@@ -160,11 +164,14 @@ def stabilizers(self, symplectic: bool = False, return_array: bool = False):
             return self._construct_operators(
                 generators[self.nqubits :],
                 phases[self.nqubits :],
+                cores=cores,
             )
 
         return self.symplectic_matrix[self.nqubits : -1, :]
 
-    def destabilizers(self, symplectic: bool = False, return_array: bool = False):
+    def destabilizers(
+        self, symplectic: bool = False, return_array: bool = False, cores: int = 1
+    ):
         """Extracts the destabilizers of the state.
 
         Args:
@@ -175,15 +182,16 @@ def destabilizers(self, symplectic: bool = False, return_array: bool = False):
                 If ``True`` returns the destabilizers as ``ndarray``.
                 If ``False``, their representation as strings is returned.
                 Defaults to ``False``.
-
+            cores (int, optional): number of processes to be used to calculate all destabilizers.
+                To be used ``symplectic=False`` and ``return_array=False``. Defaults to :math:`1`.
         Returns:
             (ndarray or list): Destabilizers of the state.
         """
         if not symplectic:
             generators, phases = self.generators(return_array)
 
             return self._construct_operators(
-                generators[: self.nqubits], phases[: self.nqubits]
+                generators[: self.nqubits], phases[: self.nqubits], cores=cores
             )
 
         return self.symplectic_matrix[: self.nqubits, :]
@@ -392,13 +400,14 @@ def copy(self, deep: bool = False):
             symplectic_matrix, self.nqubits, self.measurements, self.nshots, self.engine
         )
 
-    def _construct_operators(self, generators: list, phases: list):
+    def _construct_operators(self, generators: list, phases: list, cores: int):
         """Helper function to construct all the operators from their generators.
 
         Args:
             generators (list or ndarray): generators.
             phases (list or ndarray): phases of the generators.
-
+            cores (int, optional): number of processes to be used to construct the operators.
+                To be used when operators are strings. Defaults to :math:`1`.
         Returns:
             (list): All operators generated by the generators of the stabilizer group.
         """
@@ -426,4 +435,14 @@ def _construct_operators(self, generators: list, phases: list):
 
         operators = [(g, identity) for g in operators]
 
+        if cores > 1:
+            from multiprocessing import Pool  # pylint: disable=E0401
+
+            with Pool(cores) as pool:
+                results = pool.map(_string_product, product(*operators))
+                pool.close()
+                pool.join()
+
+            return results
+
         return [_string_product(ops) for ops in product(*operators)]