Change interferometer.

pennylane/templates/subroutines/interferometer.py

@@ -139,46 +139,48 @@ def Interferometer(theta, phi, varphi, wires, mesh="rectangular", beamsplitter="
 
     shape_varphi = _preprocess(theta, phi, varphi, wires)
 
-    if M == 1:
-        # the interferometer is a single rotation
-        Rotation(varphi[0], wires=wires[0])
-        return
-
-    n = 0  # keep track of free parameters
-
-    if mesh == "rectangular":
-        # Apply the Clements beamsplitter array
-        # The array depth is N
-        for l in range(M):
-            for k, (w1, w2) in enumerate(zip(wires[:-1], wires[1:])):
-                # skip even or odd pairs depending on layer
-                if (l + k) % 2 != 1:
-                    if beamsplitter == "clements":
-                        Rotation(phi[n], wires=Wires(w1))
-                        Beamsplitter(theta[n], 0, wires=Wires([w1, w2]))
-                    elif beamsplitter == "pennylane":
-                        Beamsplitter(theta[n], phi[n], wires=Wires([w1, w2]))
-                    else:
-                        raise ValueError(f"did not recognize beamsplitter {beamsplitter}")
-                    n += 1
-
-    elif mesh == "triangular":
-        # apply the Reck beamsplitter array
-        # The array depth is 2*N-3
-        for l in range(2 * M - 3):
-            for k in range(abs(l + 1 - (M - 1)), M - 1, 2):
-                if beamsplitter == "clements":
-                    Rotation(phi[n], wires=wires[k])
-                    Beamsplitter(theta[n], 0, wires=wires.subset([k, k + 1]))
-                elif beamsplitter == "pennylane":
-                    Beamsplitter(theta[n], phi[n], wires=wires.subset([k, k + 1]))
-                else:
-                    raise ValueError(f"did not recognize beamsplitter {beamsplitter} ")
-                n += 1
-    else:
-        raise ValueError(f"did not recognize mesh {mesh}")
-
-    # apply the final local phase shifts to all modes
-    for i in range(shape_varphi[0]):
-        act_on = wires[i]
-        Rotation(varphi[i], wires=act_on)
+    with qml.tape.OperationRecorder() as rec:
+
+        if M == 1:
+            # the interferometer is a single rotation
+            Rotation(varphi[0], wires=wires[0])
+        else:
+            n = 0  # keep track of free parameters
+
+            if mesh == "rectangular":
+                # Apply the Clements beamsplitter array
+                # The array depth is N
+                for l in range(M):
+                    for k, (w1, w2) in enumerate(zip(wires[:-1], wires[1:])):
+                        # skip even or odd pairs depending on layer
+                        if (l + k) % 2 != 1:
+                            if beamsplitter == "clements":
+                                Rotation(phi[n], wires=Wires(w1))
+                                Beamsplitter(theta[n], 0, wires=Wires([w1, w2]))
+                            elif beamsplitter == "pennylane":
+                                Beamsplitter(theta[n], phi[n], wires=Wires([w1, w2]))
+                            else:
+                                raise ValueError(f"did not recognize beamsplitter {beamsplitter}")
+                            n += 1
+
+            elif mesh == "triangular":
+                # apply the Reck beamsplitter array
+                # The array depth is 2*N-3
+                for l in range(2 * M - 3):
+                    for k in range(abs(l + 1 - (M - 1)), M - 1, 2):
+                        if beamsplitter == "clements":
+                            Rotation(phi[n], wires=wires[k])
+                            Beamsplitter(theta[n], 0, wires=wires.subset([k, k + 1]))
+                        elif beamsplitter == "pennylane":
+                            Beamsplitter(theta[n], phi[n], wires=wires.subset([k, k + 1]))
+                        else:
+                            raise ValueError(f"did not recognize beamsplitter {beamsplitter} ")
+                        n += 1
+            else:
+                raise ValueError(f"did not recognize mesh {mesh}")
+
+            # apply the final local phase shifts to all modes
+            for i in range(shape_varphi[0]):
+                act_on = wires[i]
+                Rotation(varphi[i], wires=act_on)
+    return rec.queue