Merge pull request #1139 from qiboteam/to_circuit

Add `Clifford.to_circuit` and `Clifford.copy` methods + initialization via circuits

doc/source/api-reference/qibo.rst

@@ -1420,6 +1420,10 @@ passing a symplectic matrix to the constructor.
    symplectic_matrix = backend.zero_state(nqubits=3)
    clifford = Clifford(symplectic_matrix, engine=NumpyBackend())
 
+   # The initialization above is equivalent to the initialization below
+   circuit = Circuit(nqubits=3)
+   clifford = Clifford(circuit, engine=NumpyBackend())
+
 The generators of the stabilizers can be extracted with the
 :meth:`qibo.quantum_info.clifford.Clifford.generators` method,
 or the complete set of :math:`d = 2^{n}` stabilizers operators can be extracted through the

src/qibo/backends/clifford.py

@@ -627,13 +627,15 @@ def execute_circuit(self, circuit, initial_state=None, nshots: int = 1000):
             for gate in circuit.queue:
                 state = gate.apply_clifford(self, state, nqubits)
 
-            return Clifford(
+            clifford = Clifford(
                 state,
                 measurements=circuit.measurements,
                 nshots=nshots,
                 engine=self.engine,
             )
 
+            return clifford
+
         except self.oom_error:  # pragma: no cover
             raise_error(
                 RuntimeError,