Remove RestlessMixin and deprecate restless nodes

This change removes the previously deprecated `RestlessMixin` class and
deprecates the restless processing nodes `RestlessToIQ` and
`RestlessToCounts`. The motivation for the removals is to streamline the
remaining code base. The restless features are little used and it
remains possible to set up experiments to run in restless mode by using
a custom data processor even without support in the base package.

Author: wshanks

docs/conf.py

@@ -94,7 +94,6 @@
     "manuals/verification/quantum_volume": "_images/quantum_volume_2_0.png",
     "manuals/measurement/readout_mitigation": "_images/readout_mitigation_4_0.png",
     "manuals/verification/randomized_benchmarking": "_images/randomized_benchmarking_3_1.png",
-    "manuals/measurement/restless_measurements": "_images/restless_shots.png",
     "manuals/verification/state_tomography": "_images/state_tomography_3_0.png",
     "manuals/characterization/t1": "_images/t1_0_0.png",
     "manuals/characterization/t2ramsey": "_images/t2ramsey_4_0.png",

docs/index.rst

@@ -62,7 +62,7 @@ We've divided up the documentation into four sections with different purposes:
         these manuals:
 
         * How to analyze 1- and 2-qubit errors in :doc:`randomized benchmarking </manuals/verification/randomized_benchmarking>`
-        * How to calculate the speedup from using :doc:`restless measurements </manuals/measurement/restless_measurements>`
+        * How to characterize a quantum circuit using :doc:`state tomography </manuals/verification/state_tomography>`
 
         +++
 

docs/manuals/measurement/restless_measurements.rst

@@ -62,11 +62,6 @@ Optionally, to allow configuring experiment and execution options, you can overr
             metadata["device_components"] = list(map(Resonator, self.physical_qubits))
             return metadata
 
-Furthermore, some characterization and calibration experiments can be run with restless
-measurements, i.e. measurements where the qubits are not reset and circuits are executed
-immediately after the previous measurement. Here, the :class:`.RestlessMixin` class
-can help to set the appropriate run options and data processing chain.
-
 Analysis subclassing
 --------------------
 

docs/manuals/measurement/restless_shots.png

@@ -192,8 +192,7 @@ processing connects the data returned by the backend to the data that
 the analysis classes need. Typically, you will not need to implement
 the data processing yourself since Qiskit Experiments has built-in
 methods that determine the correct instance of :class:`.DataProcessor` for
-your data. More advanced data processing includes, for example, handling
-:doc:`restless measurements </manuals/measurement/restless_measurements>`.
+your data.
 
 References
 ----------
@@ -202,8 +201,3 @@ References
     Christopher J. Wood, Ali Javadi-Abhari, David McKay, Qiskit Pulse:
     Programming Quantum Computers Through the Cloud with Pulses, Quantum
     Science and Technology **5**, 044006 (2020). https://arxiv.org/abs/2004.06755.
-
-See also
---------
-
-- Experiment manual: :doc:`/manuals/measurement/restless_measurements`

docs/tutorials/custom_experiment.rst

@@ -23,6 +23,7 @@
 from uncertainties import unumpy as unp, ufloat
 
 from qiskit.result.postprocess import format_counts_memory
+from qiskit.utils import deprecate_func
 from qiskit_experiments.data_processing.data_action import DataAction, TrainableDataAction
 from qiskit_experiments.data_processing.exceptions import DataProcessorError
 from qiskit_experiments.data_processing.discriminator import BaseDiscriminator
@@ -910,6 +911,17 @@ class RestlessNode(DataAction, ABC):
     Once the shots have been ordered in this fashion the data can be post-processed.
     """
 
+    @deprecate_func(
+        since="0.9",
+        additional_msg=(
+            "Restless data processing nodes will be removed from "
+            "qiskit-experiments. Refer to the RestlessMixin code of "
+            "qiskit-experiment 0.8 and the code for RestlessToIQ and "
+            "RestlessToCounts for the way to use a custom restless "
+            "processor on an experiment."
+        ),
+        package_name="qiskit-experiments",
+    )
     def __init__(
         self, validate: bool = True, memory_allocation: ShotOrder = ShotOrder.circuit_first
     ):

docs/tutorials/data_processor.rst

@@ -37,7 +37,7 @@ def get_kerneled_processor(
             one dimension.
         meas_return: Type of data returned by the backend, i.e., averaged data or single-shot data.
         normalize: If True then normalize the output data to the interval ``[0, 1]``.
-        pre_nodes: any nodes to be applied first in the data processing chain such as restless nodes.
+        pre_nodes: any nodes to be applied first in the data processing chain
 
     Returns:
         An instance of DataProcessor capable of processing `meas_level=MeasLevel.KERNELED` data for

qiskit_experiments/data_processing/nodes.py

@@ -130,7 +130,6 @@
 
     BackendData
     BackendTiming
-    RestlessMixin
 
 """
 from qiskit.providers.options import Options
@@ -161,4 +160,3 @@
 )
 from .json import ExperimentEncoder, ExperimentDecoder
 from .provider_interfaces import BaseJob, BaseProvider, ExtendedJob, IBMProvider, Job, Provider
-from .restless_mixin import RestlessMixin