Update for removing qutip.qip in dev.major (#146)

VQA module wrongly used the qutip.qip module, which is removed in qutip-v5.

Update the Measurement class and expand the measurement operator because calling the qutip measurement functions.

See also qutip/qutip#1890.

src/qutip_qip/circuit.py

@@ -112,9 +112,11 @@ def measurement_comp_basis(self, state):
         else:
             raise ValueError("target is not valid")
 
-        return measurement_statistics(
-            state, measurement_ops, targets=self.targets
-        )
+        measurement_ops = [
+            expand_operator(op, N=n, targets=self.targets)
+            for op in measurement_ops
+        ]
+        return measurement_statistics(state, measurement_ops)
 
     def __str__(self):
         str_name = ("Measurement(%s, target=%s, classical_store=%s)") % (

src/qutip_qip/vqa.py

@@ -3,10 +3,10 @@
 import random
 import numpy as np
 from qutip import basis, tensor, Qobj, qeye, expect
-from qutip.qip.circuit import QubitCircuit
+from qutip_qip.circuit import QubitCircuit
 from scipy.optimize import minimize
 from scipy.linalg import expm_frechet
-from qutip.qip.operations.gates import gate_sequence_product
+from qutip_qip.operations.gates import gate_sequence_product
 
 
 class VQA: