Merge pull request #1025 from qiboteam/fixrepeated

Repeated execution and density matrices
qiboteam · Oct 4, 2023 · 4792535 · 4792535
2 parents b54de78 + 1a92fed
commit 4792535
Show file tree

Hide file tree

Showing 2 changed files with 12 additions and 10 deletions.
diff --git a/src/qibo/models/circuit.py b/src/qibo/models/circuit.py
@@ -158,8 +158,9 @@ def __init__(self, nqubits, accelerators=None, density_matrix=False):
 
         self._final_state = None
         self.compiled = None
-        self.repeated_execution = False
 
+        self.has_collapse = False
+        self.has_unitary_channel = False
         self.density_matrix = density_matrix
 
         # for distributed circuits
@@ -249,13 +250,14 @@ def __add__(self, circuit):
         for gate in circuit.queue:
             newcircuit.add(gate)
 
-        # Re-execute full circuit when sampling if one of the circuits
-        # has repeated_execution ``True``
-        newcircuit.repeated_execution = (
-            self.repeated_execution or circuit.repeated_execution
-        )
         return newcircuit
 
+    @property
+    def repeated_execution(self):
+        return self.has_collapse or (
+            self.has_unitary_channel and not self.density_matrix
+        )
+
     def on_qubits(self, *qubits):
         """Generator of gates contained in the circuit acting on specified qubits.
 
@@ -591,7 +593,7 @@ def add(self, gate):
 
                 gate.result.circuit = self
                 if gate.collapse:
-                    self.repeated_execution = True
+                    self.has_collapse = True
                 else:
                     self.measurements.append(gate)
                 return gate.result
@@ -601,11 +603,11 @@ def add(self, gate):
                 for measurement in list(self.measurements):
                     if set(measurement.qubits) & set(gate.qubits):
                         measurement.collapse = True
-                        self.repeated_execution = True
+                        self.has_collapse = True
                         self.measurements.remove(measurement)
 
             if isinstance(gate, gates.UnitaryChannel):
-                self.repeated_execution = not self.density_matrix
+                self.has_unitary_channel = True
             if isinstance(gate, gates.ParametrizedGate):
                 self.parametrized_gates.append(gate)
                 if gate.trainable:

diff --git a/tests/test_models_circuit_execution.py b/tests/test_models_circuit_execution.py
@@ -64,7 +64,7 @@ def test_repeated_execute(backend, accelerators):
     c.add((gates.RY(i, t) for i, t in enumerate(thetas)))
     target_state = backend.execute_circuit(c).state(numpy=True)
     target_state = np.array(20 * [target_state])
-    c.repeated_execution = True
+    c.has_collapse = True
     final_state = backend.execute_circuit(c, nshots=20)
     final_state = [backend.to_numpy(x) for x in final_state]
     backend.assert_allclose(final_state, target_state)