Readout angle experiment

qiskit_experiments/framework/composite/composite_analysis.py

@@ -14,6 +14,7 @@
 """
 
 from typing import List, Dict
+import numpy as np
 from qiskit.result import marginal_counts
 from qiskit_experiments.framework import BaseAnalysis, ExperimentData, AnalysisResultData
 from qiskit_experiments.database_service.device_component import Qubit
@@ -159,6 +160,13 @@ def _marginalize_data(self, composite_data: List[Dict]) -> List[Dict]:
                         sub_data["counts"] = marginal_counts(datum["counts"], composite_clbits[i])
                     else:
                         sub_data["counts"] = datum["counts"]
+                if "memory" in datum:
+                    if composite_clbits is not None:
+                        sub_data["memory"] = (
+                            np.array(datum["memory"])[composite_clbits[i]]
+                        ).tolist()
+                    else:
+                        sub_data["memory"] = datum["memory"]
                 marginalized_data[index].append(sub_data)
 
         # Sort by index

qiskit_experiments/library/__init__.py

@@ -73,6 +73,7 @@
     ~characterization.Rabi
     ~characterization.EFRabi
     ~characterization.RamseyXY
+    ~characterization.ReadoutAngle
 
 
 .. _calibration:
@@ -135,6 +136,7 @@ class instance to manage parameters and pulse schedules.
     FineXAmplitude,
     FineSXAmplitude,
     RamseyXY,
+    ReadoutAngle,
 )
 from .randomized_benchmarking import StandardRB, InterleavedRB
 from .tomography import StateTomography, ProcessTomography

qiskit_experiments/library/characterization/__init__.py

@@ -36,6 +36,7 @@
     FineSXAmplitude
     RamseyXY
     RoughDrag
+    ReadoutAngle
     FineDrag
     FineXDrag
     FineSXDrag
@@ -57,6 +58,7 @@
     analysis.FineAmplitudeAnalysis
     analysis.FineXAmplitudeAnalysis
     analysis.RamseyXYAnalysis
+    analysis.ReadoutAngleAnalysis
 """
 
 from .analysis import (
@@ -69,6 +71,7 @@
     T2RamseyAnalysis,
     T1Analysis,
     CrossResonanceHamiltonianAnalysis,
+    ReadoutAngleAnalysis,
 )
 
 from .t1 import T1
@@ -81,4 +84,5 @@
 from .fine_amplitude import FineAmplitude, FineXAmplitude, FineSXAmplitude
 from .ramsey_xy import RamseyXY
 from .drag import RoughDrag
+from .readout_angle import ReadoutAngle
 from .fine_drag import FineDrag, FineXDrag, FineSXDrag

qiskit_experiments/library/characterization/analysis/__init__.py

@@ -21,3 +21,4 @@
 from .t2ramsey_analysis import T2RamseyAnalysis
 from .t1_analysis import T1Analysis
 from .cr_hamiltonian_analysis import CrossResonanceHamiltonianAnalysis
+from .readout_angle_analysis import ReadoutAngleAnalysis

qiskit_experiments/library/characterization/analysis/readout_angle_analysis.py

@@ -0,0 +1,45 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2021.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+"""
+Readout Angle Analysis class.
+"""
+
+import numpy as np
+
+from qiskit_experiments.framework import BaseAnalysis, AnalysisResultData
+
+
+class ReadoutAngleAnalysis(BaseAnalysis):
+    """
+    A class to analyze readout angle experiments
+    """
+
+    # pylint: disable=unused-argument
+    def _run_analysis(self, experiment_data, **kwargs):
+        angles = []
+        for i in range(2):
+            center = complex(*experiment_data.data(i)["memory"][0])
+            angles.append(np.angle(center))
+
+        angle = (angles[0] + angles[1]) / 2
+        if (np.abs(angles[0] - angles[1])) % (2 * np.pi) > np.pi:
+            angle += np.pi
+
+        analysis_results = [
+            AnalysisResultData(
+                name="ReadoutAngle",
+                value=angle,
+                extra={"angle_ground": angles[0], "angle_excited": angles[1]},
+            )
+        ]
+
+        return analysis_results, []

qiskit_experiments/library/characterization/readout_angle.py

@@ -0,0 +1,101 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2021.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+"""
+Readout Angle Experiment class.
+"""
+
+from typing import List, Optional
+
+from qiskit.circuit import QuantumCircuit
+from qiskit.qobj.utils import MeasLevel
+from qiskit.providers.backend import Backend
+
+from qiskit_experiments.framework import BaseExperiment, Options
+from qiskit_experiments.library.characterization.analysis.readout_angle_analysis import (
+    ReadoutAngleAnalysis,
+)
+
+
+class ReadoutAngle(BaseExperiment):
+    r"""
+    Readout angle experiment class
+
+    # section: overview
+
+        Design and analyze experiments for estimating readout angle of the qubit.
+        The readout angle is the average of two angles: the angle of the IQ
+        cluster center of the ground state, and the angle of the IQ cluster center
+        of the excited state.
+
+        Each experiment consists of the following steps:
+
+        1. Circuits generation: two circuits, the first circuit measures the qubit
+        in the ground state, the second circuit sets the qubit in the excited state
+        and measures it. Measurements are in level 1 (kerneled).
+
+        2. Backend execution: actually running the circuits on the device
+        (or a simulator that supports level 1 measurements). The backend returns
+        the cluster centers of the ground and excited states.
+
+        3. Analysis of results: return the average of the angles of the two centers.
+
+    """
+
+    __analysis_class__ = ReadoutAngleAnalysis
+
+    @classmethod
+    def _default_run_options(cls) -> Options:
+        """Default run options."""
+        options = super()._default_run_options()
+
+        options.meas_level = MeasLevel.KERNELED
+        options.meas_return = "avg"
+
+        return options
+
+    def __init__(
+        self,
+        qubit: int,
+        backend: Optional[Backend] = None,
+    ):
+        """
+        Initialize the readout angle experiment class
+
+        Args:
+            qubit: the qubit whose readout angle is to be estimated
+            backend: Optional, the backend to run the experiment on.
+        """
+        # Initialize base experiment
+        super().__init__([qubit], backend=backend)
+
+    def circuits(self) -> List[QuantumCircuit]:
+        """
+        Return a list of experiment circuits
+
+        Returns:
+            The experiment circuits
+        """
+        circ0 = QuantumCircuit(1, 1)
+        circ0.measure(0, 0)
+
+        circ1 = QuantumCircuit(1, 1)
+        circ1.x(0)
+        circ1.measure(0, 0)
+
+        for i, circ in enumerate([circ0, circ1]):
+            circ.metadata = {
+                "experiment_type": self._type,
+                "qubit": self.physical_qubits[0],
+                "xval": i,
+            }
+
+        return [circ0, circ1]

releasenotes/notes/readout-angle-4d3be1d584ba5ac1.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    A new readout angle experiment. The experiment computes the average of the angles of the IQ clusters of the ground and excited states.

test/test_readout_angle.py

@@ -0,0 +1,51 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2021.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+"""
+Test readout angle experiment
+"""
+
+import numpy as np
+
+from qiskit.test import QiskitTestCase
+from qiskit_experiments.library import ReadoutAngle
+from qiskit_experiments.test.mock_iq_backend import MockIQBackend
+
+
+class ReadoutAngleBackend(MockIQBackend):
+    """
+    Mock IQ backend tailored to the readout angle test
+    """
+
+    def _compute_probability(self, circuit):
+        return 1 - circuit.metadata["xval"]
+
+
+class TestReadoutAngle(QiskitTestCase):
+    """
+    Test the readout angle experiment
+    """
+
+    def test_readout_angle_end2end(self):
+        """
+        Test readout angle experiment using a simulator.
+        """
+        backend = ReadoutAngleBackend(iq_cluster_centers=(5.0, 5.0, -3.0, 3.0))
+        exp = ReadoutAngle(0)
+        expdata = exp.run(backend, shots=100000).block_for_results()
+        res = expdata.analysis_results(0)
+        self.assertAlmostEqual(res.value % (2 * np.pi), np.pi / 2, places=2)
+
+        backend = ReadoutAngleBackend(iq_cluster_centers=(5.0, 5.0, 0, -3.0))
+        exp = ReadoutAngle(0)
+        expdata = exp.run(backend, shots=100000).block_for_results()
+        res = expdata.analysis_results(0)
+        self.assertAlmostEqual(res.value % (2 * np.pi), 15 * np.pi / 8, places=2)