refactor: Review MitEx

qermit/taskgraph/mitex.py

@@ -93,8 +93,12 @@ def get_basic_measurement_circuit(
     :param string: Qubit Pauli String to be measured
     :type string: QubitPauliString
 
-    :return: Measurement circuit for appending on some ansatz
-    :rtype: Circuit
+    :return: Tuple of measurement circuit for appending on some ansatz
+        and MeasurementInfo. Each entry of th measurement information
+        contains a QubitPauliString, the bits required to take expectation
+        over in resulting result and a bool signifying whether expectation
+        should be inverted when taking result.
+    :rtype: Tuple[Circuit, MeasurementInfo]
     """
     measurement_circuit = Circuit()
     measured_qbs = []
@@ -152,11 +156,11 @@ def task(
                 circ = circuit.copy()
                 # tuple, first entry is measurement circuit for appending
                 # second entry is MeasurementInfo for deriving expectation
-                measurement_circuit = get_basic_measurement_circuit(string)
-                circ.append(measurement_circuit[0])
+                measurement_circuit, measurement_info = get_basic_measurement_circuit(string)
+                circ.append(measurement_circuit)
                 # add new circuit to observable tracker
                 observable_tracker.add_measurement_circuit(
-                    MeasurementCircuit(circ, symbols), [measurement_circuit[1]]
+                    MeasurementCircuit(circ, symbols), [measurement_info]
                 )
 
             # retrieve all measurement circuits, substitute symbols

qermit/taskgraph/utils.py

@@ -403,10 +403,11 @@ def check_string(self, string: QubitPauliString) -> bool:
         """
         if string not in self._qps_to_indices:
             return False
+
         if len(self._qps_to_indices[string]) > 0:
             return True
-        else:
-            return False
+
+        return False
 
     def get_empty_strings(self) -> List[QubitPauliString]:
         """

tests/mitex_test.py

@@ -15,7 +15,7 @@
 
 import copy
 
-from pytket.circuit import Circuit, OpType, Qubit, fresh_symbol  # type: ignore
+from pytket.circuit import Bit, Circuit, OpType, Qubit, fresh_symbol  # type: ignore
 from pytket.extensions.qiskit import AerBackend  # type: ignore
 from pytket.pauli import Pauli, QubitPauliString  # type: ignore
 from pytket.utils import QubitPauliOperator
@@ -32,11 +32,63 @@
     collate_circuit_shots_task_gen,
     filter_observable_tracker_task_gen,
     gen_compiled_shot_split_MitRes,
+    get_basic_measurement_circuit,
     get_expectations_task_gen,
     split_results_task_gen,
 )
 
 
+def test_get_basic_measurement_circuit() -> None:
+
+    q_0 = Qubit(name="test qubits a", index=0)
+    q_1 = Qubit(name="test qubits a", index=1)
+    q_2 = Qubit(name="test qubits b", index=0)
+    q_3 = Qubit(name="test qubits b", index=1)
+
+    qps_0 = QubitPauliString([q_1, q_2, q_3], [Pauli.Z, Pauli.X, Pauli.I])
+
+    circuit = Circuit()
+
+    circuit.add_qubit(q_1)
+    circuit.add_bit(Bit(0))
+    circuit.Measure(q_1, Bit(0))
+
+    circuit.add_qubit(q_2)
+    circuit.H(q_2)
+    circuit.add_bit(Bit(1))
+    circuit.Measure(q_2, Bit(1))
+
+    measurement_circuit, (string, bits, meas_bool) = get_basic_measurement_circuit(qps_0)
+    assert measurement_circuit == circuit
+    assert bits == [Bit(0), Bit(1)]
+    assert not meas_bool
+    assert string == qps_0
+
+    qps_1 = QubitPauliString([q_0, q_2, q_1], [Pauli.Z, Pauli.Y, Pauli.X])
+
+    circuit = Circuit()
+
+    circuit.add_qubit(q_0)
+    circuit.add_bit(Bit(0))
+    circuit.Measure(q_0, Bit(0))
+
+    circuit.add_qubit(q_1)
+    circuit.add_bit(Bit(1))
+    circuit.H(q_1)
+    circuit.Measure(q_1, Bit(1))
+
+    circuit.add_qubit(q_2)
+    circuit.add_bit(Bit(2))
+    circuit.Rx(0.5, q_2)
+    circuit.Measure(q_2, Bit(2))
+
+    measurement_circuit, (string, bits, meas_bool) = get_basic_measurement_circuit(qps_1)
+    assert measurement_circuit == circuit
+    assert bits == [Bit(0), Bit(1), Bit(2)]
+    assert not meas_bool
+    assert string == qps_1
+
+
 def test_mitex_cache():
     circuit = Circuit(1).X(0)
     backend = AerBackend()