Test gate copy perf

tangelo/linq/circuit.py

@@ -128,13 +128,14 @@ def is_mixed_state(self):
         """
         return "MEASURE" in self.counts
 
-    def add_gate(self, gate):
+    def add_gate(self, g):
         """Add a new gate to a circuit object and update other fields of the
         circuit object to gradually keep track of its properties (gate count,
         qubit indices...).
         """
-        # Add the gate to the list of gates
-        self._gates += [gate]
+        # Add a copy of the gate to the list of gates
+        gate = Gate(g.name, g.target, g.control, g.parameter, g.is_variational)
+        self._gates.append(gate)
 
         # A circuit is variational as soon as a variational gate is added to it
         if gate.is_variational:

tangelo/linq/tests/test_circuits.py

@@ -59,6 +59,21 @@ def test_is_variational(self):
         self.assertTrue(circuit1.is_variational is False)
         self.assertTrue(circuit3.is_variational is True)
 
+    def test_gate_data_is_copied(self):
+        """ Ensure that circuit is not referencing mutable variables that could cause it to change after
+        instantiation if the values of the variables are later changed in external code. """
+
+        mygates2 = copy.deepcopy(mygates)
+        c1 = Circuit(mygates2)
+
+        g = mygates2[0]
+        g.target.append(1)
+        g.name = 'POTATO'
+        g.parameter = -999.
+
+        c2 = Circuit(mygates2)
+        self.assertTrue(c1 != c2)
+
     def test_width(self):
         """ Ensure the width attribute of the circuit object (number of qubits) matches the gate operations
         present in the circuit. """