Remove unnecessary circuit metadata (#1315)

### Summary As the number of qubits in the parallel experiment increases, the memory footprint of job payload communicated through wire becomes more serious issue. Some built-in experiment generates circuits with unnecessary metadata, which is - duplicated information existing in experiment metadata - duplicated information existing in every circuit metadata - un-used information in analysis This PR removes such unnecessary fields from the circuit metadata to reduce payload size. For example, if an experiment is paired with a curve analysis, it only requires `xval` and other minimum keys necessary for model matching. ### Details and comments Tutorial is also updated. --------- Co-authored-by: Will Shanks <[email protected]> Co-authored-by: Helena Zhang <[email protected]>
qiskit-community · Jan 10, 2024 · 79e0a69 · 79e0a69
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diff --git a/docs/manuals/characterization/t1.rst b/docs/manuals/characterization/t1.rst
@@ -98,11 +98,10 @@ that is close to a logical value '0'.
     mu = 1e-6
 
     # qubit properties
-    t1 = [45 * mu, 45 * mu]
-    t2 = [value/2 for value in t1]
+    t1 = 45 * mu
 
     # we will guess that our guess is 10% off the exact value of t1 for qubit 0.
-    t1_estimated_shift = t1[0]/10
+    t1_estimated_shift = t1/10
 
     # We use log space for the delays because of the noise properties
     delays = np.logspace(1, 11, num=23, base=np.exp(1))
@@ -111,25 +110,28 @@ that is close to a logical value '0'.
     # Adding circuits with delay=0 and long delays so the centers in the IQ plane won't be misplaced.
     # Without this, the fitting can provide wrong results.
     delays = np.insert(delays, 0, 0)
-    delays = np.append(delays, [t1[0]*3])
+    delays = np.append(delays, [t1*3])
 
     num_qubits = 2
     num_shots = 2048
 
     backend = MockIQBackend(
-        MockIQT1Helper(t1=t1, iq_cluster_centers=[((-5.0, -4.0), (-5.0, 4.0)), ((3.0, 1.0), (5.0, -3.0))]
-                           , iq_cluster_width=[1.0, 2.0])
+        MockIQT1Helper(
+            t1=t1,
+            iq_cluster_centers=[((-5.0, -4.0), (-5.0, 4.0)), ((3.0, 1.0), (5.0, -3.0))],
+            iq_cluster_width=[1.0, 2.0],
+        )
     )
 
     # Creating a T1 experiment
     expT1_kerneled = T1((0,), delays)
     expT1_kerneled.analysis = T1KerneledAnalysis()
-    expT1_kerneled.analysis.set_options(p0={"amp": 1, "tau": t1[0] + t1_estimated_shift, "base": 0})
+    expT1_kerneled.analysis.set_options(p0={"amp": 1, "tau": t1 + t1_estimated_shift, "base": 0})
 
     # Running the experiment
-    expdataT1_kerneled = expT1_kerneled.run(backend=backend, meas_return="avg",
-                                            meas_level=MeasLevel.KERNELED,
-                                            shots=num_shots).block_for_results()
+    expdataT1_kerneled = expT1_kerneled.run(
+        backend=backend, meas_return="avg", meas_level=MeasLevel.KERNELED, shots=num_shots
+    ).block_for_results()
 
     # Displaying results
     display(expdataT1_kerneled.figure(0))

diff --git a/docs/tutorials/custom_experiment.rst b/docs/tutorials/custom_experiment.rst
@@ -365,6 +365,19 @@ signature to restore the output to what it should be without the random Pauli fr
 at the end. We make a new :class:`.AnalysisResultData` object since we're rewriting the 
 counts from the original experiment.
 
+.. note::
+
+    As you may find here, circuit metadata is mainly used to generate a structured data
+    in the analysis class for convenience of result handling.
+    A metadata supplied to a particular circuit should appear in the corresponding
+    experiment result data dictionary stored in the experiment data.
+    If you attach large amount of metadata which is not expected to be used in the analysis,
+    the metadata just unnecessarily increases the job payload memory footprint,
+    and it prevents your experiment class from scaling in qubit size through
+    the composite experiment tooling.
+    If you still want to store some experiment setting, which is common to all circuits
+    or irrelevant to the analysis, use the experiment metadata instead.
+
 .. jupyter-input::
 
     from qiskit_experiments.framework import BaseAnalysis, AnalysisResultData

diff --git a/qiskit_experiments/library/characterization/drag.py b/qiskit_experiments/library/characterization/drag.py
@@ -171,8 +171,6 @@ def circuits(self) -> List[QuantumCircuit]:
                 assigned_circuit = circuit.assign_parameters({beta: beta_val}, inplace=False)
 
                 assigned_circuit.metadata = {
-                    "experiment_type": self._type,
-                    "qubits": self.physical_qubits,
                     "xval": beta_val,
                     "nrep": rep,
                 }

diff --git a/qiskit_experiments/library/characterization/fine_amplitude.py b/qiskit_experiments/library/characterization/fine_amplitude.py
@@ -162,10 +162,7 @@ def _spam_cal_circuits(self, meas_circuit: QuantumCircuit) -> List[QuantumCircui
             circ.compose(meas_circuit, inplace=True)
 
             circ.metadata = {
-                "experiment_type": self._type,
-                "qubits": self.physical_qubits,
                 "xval": add_x,
-                "unit": "gate number",
                 "series": "spam-cal",
             }
 
@@ -229,10 +226,7 @@ def circuits(self) -> List[QuantumCircuit]:
             circuit.compose(meas_circ, qubits, range(meas_circ.num_clbits), inplace=True)
 
             circuit.metadata = {
-                "experiment_type": self._type,
-                "qubits": self.physical_qubits,
                 "xval": repetition,
-                "unit": "gate number",
                 "series": 1,
             }
 

diff --git a/qiskit_experiments/library/characterization/fine_drag.py b/qiskit_experiments/library/characterization/fine_drag.py
@@ -218,12 +218,7 @@ def circuits(self) -> List[QuantumCircuit]:
                     params=[],
                 )
 
-            circuit.metadata = {
-                "experiment_type": self._type,
-                "qubits": self.physical_qubits,
-                "xval": repetition,
-                "unit": "gate number",
-            }
+            circuit.metadata = {"xval": repetition}
 
             circuits.append(circuit)
 

diff --git a/qiskit_experiments/library/characterization/fine_frequency.py b/qiskit_experiments/library/characterization/fine_frequency.py
@@ -127,12 +127,7 @@ def circuits(self) -> List[QuantumCircuit]:
             circuit.sx(0)
             circuit.measure_all()
 
-            circuit.metadata = {
-                "experiment_type": self._type,
-                "qubits": self.physical_qubits,
-                "xval": repetition,
-                "unit": "Number of delays",
-            }
+            circuit.metadata = {"xval": repetition}
 
             circuits.append(circuit)
 

diff --git a/qiskit_experiments/library/characterization/half_angle.py b/qiskit_experiments/library/characterization/half_angle.py
@@ -160,12 +160,7 @@ def circuits(self) -> List[QuantumCircuit]:
             circuit.sx(0)
             circuit.measure_all()
 
-            circuit.metadata = {
-                "experiment_type": self._type,
-                "qubits": self.physical_qubits,
-                "xval": repetition,
-                "unit": "repetition number",
-            }
+            circuit.metadata = {"xval": repetition}
 
             circuits.append(circuit)
 

diff --git a/qiskit_experiments/library/characterization/qubit_spectroscopy.py b/qiskit_experiments/library/characterization/qubit_spectroscopy.py
@@ -123,7 +123,7 @@ def circuits(self):
             freq_shift = np.round(freq_shift, decimals=3)
 
             assigned_circ = circuit.assign_parameters({freq_param: freq_shift}, inplace=False)
-            self._add_metadata(assigned_circ, freq, sched)
+            self._add_metadata(assigned_circ, freq)
 
             circs.append(assigned_circ)
 

diff --git a/qiskit_experiments/library/characterization/rabi.py b/qiskit_experiments/library/characterization/rabi.py
@@ -163,13 +163,7 @@ def circuits(self) -> List[QuantumCircuit]:
             # which isn't serializable in the metadata.
             amp = float(np.round(amp, decimals=6))
             assigned_circ = circuit.assign_parameters({param: amp}, inplace=False)
-            assigned_circ.metadata = {
-                "experiment_type": self._type,
-                "qubits": self.physical_qubits,
-                "xval": amp,
-                "unit": "arb. unit",
-                "amplitude": amp,
-            }
+            assigned_circ.metadata = {"xval": amp}
 
             circs.append(assigned_circ)
 

diff --git a/qiskit_experiments/library/characterization/ramsey_xy.py b/qiskit_experiments/library/characterization/ramsey_xy.py
@@ -155,42 +155,35 @@ def circuits(self) -> List[QuantumCircuit]:
             rotation_angle = rotation_angle * timing.dt
 
         # Create the X and Y circuits.
-        metadata = {
-            "experiment_type": self._type,
-            "qubits": self.physical_qubits,
-            "osc_freq": self.experiment_options.osc_freq,
-            "unit": "s",
-        }
-
         ram_x = self._pre_circuit()
         ram_x.sx(0)
         ram_x.delay(p_delay, 0, timing.delay_unit)
         ram_x.rz(rotation_angle, 0)
         ram_x.sx(0)
         ram_x.measure_active()
-        ram_x.metadata = metadata.copy()
 
         ram_y = self._pre_circuit()
         ram_y.sx(0)
         ram_y.delay(p_delay, 0, timing.delay_unit)
         ram_y.rz(rotation_angle - np.pi / 2, 0)
         ram_y.sx(0)
         ram_y.measure_active()
-        ram_y.metadata = metadata.copy()
 
         circs = []
         for delay in self.experiment_options.delays:
-            assigned_x = ram_x.assign_parameters(
-                {p_delay: timing.round_delay(time=delay)}, inplace=False
-            )
-            assigned_x.metadata["series"] = "X"
-            assigned_x.metadata["xval"] = timing.delay_time(time=delay)
-
-            assigned_y = ram_y.assign_parameters(
-                {p_delay: timing.round_delay(time=delay)}, inplace=False
-            )
-            assigned_y.metadata["series"] = "Y"
-            assigned_y.metadata["xval"] = timing.delay_time(time=delay)
+            delay_dt = timing.round_delay(time=delay)
+            delay_sec = timing.delay_time(time=delay)
+
+            assigned_x = ram_x.assign_parameters({p_delay: delay_dt}, inplace=False)
+            assigned_x.metadata = {
+                "series": "X",
+                "xval": delay_sec,
+            }
+            assigned_y = ram_y.assign_parameters({p_delay: delay_dt}, inplace=False)
+            assigned_y.metadata = {
+                "series": "Y",
+                "xval": delay_sec,
+            }
 
             circs.extend([assigned_x, assigned_y])
 

diff --git a/qiskit_experiments/library/characterization/readout_angle.py b/qiskit_experiments/library/characterization/readout_angle.py
@@ -85,16 +85,11 @@ def circuits(self) -> List[QuantumCircuit]:
         """
         circ0 = QuantumCircuit(1, 1)
         circ0.measure(0, 0)
+        circ0.metadata = {"xval": 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,
-            }
+        circ1.metadata = {"xval": 1}
 
         return [circ0, circ1]
diff --git a/qiskit_experiments/library/characterization/resonator_spectroscopy.py b/qiskit_experiments/library/characterization/resonator_spectroscopy.py
@@ -283,7 +283,7 @@ def circuits(self):
 
             circuit = self._template_circuit()
             circuit.add_calibration("measure", self.physical_qubits, sched_)
-            self._add_metadata(circuit, freq, sched)
+            self._add_metadata(circuit, freq)
 
             circs.append(circuit)
 

diff --git a/qiskit_experiments/library/characterization/spectroscopy.py b/qiskit_experiments/library/characterization/spectroscopy.py
@@ -17,7 +17,6 @@
 
 import numpy as np
 from qiskit import QuantumCircuit
-from qiskit import pulse
 from qiskit.exceptions import QiskitError
 from qiskit.providers import Backend
 from qiskit.qobj.utils import MeasLevel
@@ -109,19 +108,13 @@ def _backend_center_frequency(self) -> float:
         which depends on the nature of the spectroscopy experiment.
         """
 
-    def _add_metadata(self, circuit: QuantumCircuit, freq: float, sched: pulse.ScheduleBlock):
+    def _add_metadata(self, circuit: QuantumCircuit, freq: float):
         """Helper method to add the metadata to avoid code duplication with subclasses."""
 
         if not self._absolute:
             freq += self._backend_center_frequency
 
-        circuit.metadata = {
-            "experiment_type": self._type,
-            "qubits": self.physical_qubits,
-            "xval": np.round(freq, decimals=3),
-            "unit": "Hz",
-            "schedule": str(sched),
-        }
+        circuit.metadata = {"xval": np.round(freq, decimals=3)}
 
     def _metadata(self):
         metadata = super()._metadata()

diff --git a/qiskit_experiments/library/characterization/t1.py b/qiskit_experiments/library/characterization/t1.py
@@ -105,12 +105,7 @@ def circuits(self) -> List[QuantumCircuit]:
             circ.barrier(0)
             circ.measure(0, 0)
 
-            circ.metadata = {
-                "experiment_type": self._type,
-                "qubit": self.physical_qubits[0],
-                "unit": "s",
-            }
-            circ.metadata["xval"] = timing.delay_time(time=delay)
+            circ.metadata = {"xval": timing.delay_time(time=delay)}
 
             circuits.append(circ)
 

diff --git a/qiskit_experiments/library/characterization/t2hahn.py b/qiskit_experiments/library/characterization/t2hahn.py
@@ -131,18 +131,12 @@ def circuits(self) -> List[QuantumCircuit]:
         """
         timing = BackendTiming(self.backend)
 
-        template = QuantumCircuit(1, 1)
-        template.metadata = {
-            "experiment_type": self._type,
-            "qubit": self.physical_qubits[0],
-            "unit": "s",
-        }
-
         delay_param = Parameter("delay")
 
         num_echoes = self.experiment_options.num_echoes
 
         # First X rotation in 90 degrees
+        template = QuantumCircuit(1, 1)
         template.rx(np.pi / 2, 0)  # Brings the qubit to the X Axis
         if num_echoes == 0:
             # if number of echoes is 0 then just apply the delay gate
@@ -174,7 +168,7 @@ def circuits(self) -> List[QuantumCircuit]:
             assigned = template.assign_parameters(
                 {delay_param: timing.round_delay(time=single_delay)}, inplace=False
             )
-            assigned.metadata["xval"] = total_delay
+            assigned.metadata = {"xval": total_delay}
             circuits.append(assigned)
 
         return circuits

diff --git a/qiskit_experiments/library/characterization/t2ramsey.py b/qiskit_experiments/library/characterization/t2ramsey.py
@@ -125,13 +125,7 @@ def circuits(self) -> List[QuantumCircuit]:
             circ.barrier(0)
             circ.measure(0, 0)
 
-            circ.metadata = {
-                "experiment_type": self._type,
-                "qubit": self.physical_qubits[0],
-                "xval": timing.delay_time(time=delay),
-                "osc_freq": self.experiment_options.osc_freq,
-                "unit": "s",
-            }
+            circ.metadata = {"xval": timing.delay_time(time=delay)}
 
             circuits.append(circ)
 
@@ -144,4 +138,5 @@ def _metadata(self):
         for run_opt in ["meas_level", "meas_return"]:
             if hasattr(self.run_options, run_opt):
                 metadata[run_opt] = getattr(self.run_options, run_opt)
+        metadata["osc_freq"] = self.experiment_options.osc_freq
         return metadata
diff --git a/qiskit_experiments/library/characterization/zz_ramsey.py b/qiskit_experiments/library/characterization/zz_ramsey.py
@@ -221,10 +221,6 @@ def _template_circuits(
         Returns:
             Circuits for series 0 and 1
         """
-        metadata = {
-            "unit": "s",
-        }
-
         delay = Parameter("delay")
 
         timing = BackendTiming(self.backend)
@@ -244,7 +240,7 @@ def _template_circuits(
 
         # Template circuit for series 0
         # Control qubit starting in |0> state, flipping to |1> in middle
-        circ0 = QuantumCircuit(2, 1, metadata=metadata.copy())
+        circ0 = QuantumCircuit(2, 1)
         circ0.metadata["series"] = "0"
 
         circ0.sx(0)
@@ -271,7 +267,7 @@ def _template_circuits(
 
         # Template circuit for series 1
         # Control qubit starting in |1> state, flipping to |0> in middle
-        circ1 = QuantumCircuit(2, 1, metadata=metadata.copy())
+        circ1 = QuantumCircuit(2, 1)
         circ1.metadata["series"] = "1"
 
         circ1.x(1)

diff --git a/qiskit_experiments/library/quantum_volume/qv_experiment.py b/qiskit_experiments/library/quantum_volume/qv_experiment.py
@@ -167,10 +167,8 @@ def circuits(self) -> List[QuantumCircuit]:
             qv_circ = QuantumVolumeCircuit(depth, depth, seed=rng)
             qv_circ.measure_active()
             qv_circ.metadata = {
-                "experiment_type": self._type,
                 "depth": depth,
                 "trial": trial,
-                "qubits": self.physical_qubits,
                 "ideal_probabilities": self._get_ideal_data(qv_circ),
             }
             circuits.append(qv_circ)