Fine amplitude fix (#698)

* Fixes an issue with fine amplitude where the measurement was not applied on the logical qubit (i.e. before intial mapping).

Author: eggerdj

qiskit_experiments/library/characterization/fine_amplitude.py

@@ -124,10 +124,16 @@ def __init__(
             qubits: The qubit(s) on which to run the fine amplitude calibration experiment.
             gate: The gate that will be repeated.
             backend: Optional, the backend to run the experiment on.
+            measurement_qubits: The qubits in the given physical qubits that need to
+                be measured.
         """
         super().__init__(qubits, analysis=FineAmplitudeAnalysis(), backend=backend)
         self.set_experiment_options(gate=gate)
-        self._measurement_qubits = measurement_qubits or qubits
+
+        if measurement_qubits is not None:
+            self._measurement_qubits = [self.physical_qubits.index(q) for q in measurement_qubits]
+        else:
+            self._measurement_qubits = range(self.num_qubits)
 
     def _spam_cal_circuits(self, meas_circuit: QuantumCircuit) -> List[QuantumCircuit]:
         """This method returns the calibration circuits.
@@ -344,7 +350,7 @@ def __init__(self, qubits: Sequence[int], backend: Optional[Backend] = None):
         # Failing to do so causes issues with QuantumCircuit.calibrations.
         gate = Gate("szx", 2, [])
 
-        super().__init__(qubits, gate, backend=backend, measurement_qubits=[1])
+        super().__init__(qubits, gate, backend=backend, measurement_qubits=[qubits[1]])
         # Set default analysis options
         self.analysis.set_options(
             angle_per_gate=np.pi / 2,

test/calibration/experiments/test_fine_amplitude.py

@@ -148,6 +148,7 @@ def test_x90p(self):
             self.assertEqual(circ.count_ops().get("sx", 0), expected[idx])
 
 
+@ddt
 class TestSpecializations(QiskitExperimentsTestCase):
     """Test the options of the specialized classes."""
 
@@ -174,6 +175,16 @@ def test_fine_sx_amp(self):
         self.assertEqual(exp.analysis.options.phase_offset, np.pi)
         self.assertEqual(exp.experiment_options.gate, SXGate())
 
+    @data((2, 3), (3, 1), (0, 1))
+    def test_measure_qubits(self, qubits):
+        """Test that the measurement is on the logical qubits."""
+
+        fine_amp = FineZXAmplitude(qubits)
+        for circuit in fine_amp.circuits():
+            self.assertEqual(circuit.num_qubits, 2)
+            self.assertEqual(circuit.data[-1][0].name, "measure")
+            self.assertEqual(circuit.data[-1][1][0], circuit.qregs[0][1])
+
 
 class TestFineAmplitudeCal(QiskitExperimentsTestCase):
     """A class to test the fine amplitude calibration experiments."""