Merge pull request #47 from thisac/fix-cond-not-propagating

Fix conditional not propagating with parametric ops

dwave/gate/circuit.py

@@ -208,7 +208,7 @@ def append(self, operation: Operation) -> None:
             # if a parametric operation is called within a non-parameteric circuit, all variables
             # should be replaced by their corresponding parameter values; eval does that
             eval = getattr(operation, "eval", None)
-            operation = eval() if eval else operation
+            operation = eval(inplace=True) if eval else operation
 
         for q in operation.qubits or []:
             if q not in self.qubits:

releasenotes/notes/fix-cond-not-propagating-5dd63d14836aa27e.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Updates the circuit so that conditional parametric gates are evaluated in place when appended to
+    the active circuit, fixing an issue where changes to these gates post application are not
+    propagated to the circuit.

tests/test_simulator/test_measurements.py

@@ -210,6 +210,9 @@ def test_conditional_op_multiple_qubits_false(self):
         assert np.allclose(circuit.state, expected)
         assert x.is_blocked
 
+        # assert that the returned op is the circuit op
+        assert x is circuit.circuit[-1]
+
     def test_conditional_op_multiple_qubits_true(self):
         """Test simulating a circuit with a multiple conditional ops (true)."""
         circuit = Circuit(2, 2)
@@ -227,6 +230,46 @@ def test_conditional_op_multiple_qubits_true(self):
         assert np.allclose(circuit.state, expected)
         assert not x.is_blocked
 
+        # assert that the returned op is the circuit op
+        assert x is circuit.circuit[-1]
+
+    def test_conditional_op_parametric_false(self):
+        """Test simulating a circuit with a conditional parametric op (false)."""
+        circuit = Circuit(2, 1)
+
+        with circuit.context as (q, c):
+            ops.Measurement(q[0]) | c[0]  # state is |00>
+            rx = ops.RX(np.pi, q[1]).conditional(c[0])
+
+        simulate(circuit)
+        # should NOT apply X on qubit 1 leaving state in |00>
+        expected = np.array([1, 0, 0, 0])
+
+        assert np.allclose(circuit.state, expected)
+        assert rx.is_blocked
+
+        # assert that the returned op is the circuit op
+        assert rx is circuit.circuit[-1]
+
+    def test_conditional_op_parametric_true(self):
+        """Test simulating a circuit with a conditional parametric op (true)."""
+        circuit = Circuit(2, 1)
+
+        with circuit.context as (q, c):
+            ops.X(q[0])
+            ops.Measurement(q[0]) | c[0]  # state is |10>
+            rx = ops.RX(np.pi, q[1]).conditional(c[0])
+
+        simulate(circuit)
+        # should apply RX(pi) on qubit 1 changing state to |11> (with extra global phase)
+        expected = np.array([0, 0, 0, -1j])
+
+        assert np.allclose(circuit.state, expected)
+        assert not rx.is_blocked
+
+        # assert that the returned op is the circuit op
+        assert rx is circuit.circuit[-1]
+
     def test_bell_state_measurement(self):
         """Test that measurement gives one of two correct states and sets the resulting
         state vector correctly for the Bell state."""