Note
This is the documentation for the current state of the development branch of Qiskit Experiments. The documentation or APIs here can change prior to being released.
LocalReadoutError¶
- class LocalReadoutError(physical_qubits=None, backend=None)[source]¶
An experiment for characterizing local readout error.
Overview
This class constructs a
LocalReadoutMitigator
containing a sequence of assignment matrices \(A\) characterizing the readout error for the given qubits from the experiment results. The full assignment matrix is accessible via theassignment_matrix()
method.Readout errors affect quantum computation during the measurement of the qubits in a quantum device. By characterizing the readout errors, it is possible to construct a readout error mitigator that is used both to obtain a more accurate distribution of the outputs, and more accurate measurements of expectation value for measurables.
The readout mitigator is generated from an assignment matrix: a \(2^n \times 2^n\) matrix \(A\) such that \(A_{y,x}\) is the probability to observe \(y\) given the true outcome should be \(x\). The assignment matrix is used to compute the mitigation matrix used in the readout error mitigation process itself.
A Local readout mitigator works under the assumption that readout errors are mostly local, meaning readout errors for different qubits are independent of each other. In this case, the assignment matrix is the tensor product of \(n\) \(2 \times 2\) matrices, one for each qubit, making it practical to store the assignment matrix in implicit form, by storing the individual \(2 \times 2\) assignment matrices. The corresponding class in Qiskit is the
LocalReadoutMitigator
inqiskit.result
.The experiment generates 2 circuits, corresponding to the states \(|0^n\rangle\) and \(|1^n\rangle\), measuring the error in all the qubits at once, and constructs the assignment matrix and local mitigator from the results.
See
LocalReadoutErrorAnalysis
documentation for additional information on local readout error experiment analysis.References
[1] Sergey Bravyi, Sarah Sheldon, Abhinav Kandala, David C. Mckay, Jay M. Gambetta, Mitigating measurement errors in multi-qubit experiments, Phys. Rev. A 103, 042605 (2021), doi: 10.1103/PhysRevA.103.042605 (open)
User manual
Analysis class reference
Experiment options
These options can be set by the
set_experiment_options()
method.- Options
Defined in the class
BaseExperiment
:max_circuits (Optional[int])
Default value:None
The maximum number of circuits per job when running an experiment on a backend.
Example
from qiskit_experiments.library import LocalReadoutError qubits = list(range(4)) exp = LocalReadoutError(physical_qubits=qubits, backend=backend) exp.analysis.set_options(plot=True) exp.set_run_options(shots=10000) exp_data = exp.run().block_for_results() display(exp_data.figure(0)) exp_data.analysis_results(dataframe=True)
name experiment components value quality backend run_time 319efc17 Local Readout Mitigator LocalReadoutError [Q0, Q1, Q2, Q3] <qiskit.result.mitigation.local_readout_mitiga... None aer_simulator_from(fake_perth) None Initialization
Initialize a local readout error characterization experiment.
- Parameters:
physical_qubits (Iterable[int] | None) – Optional, the backend qubits being characterized for readout error. If None all qubits on the provided backend will be characterized.
backend (Backend | None) – Optional, the backend to characterize.
- Raises:
QiskitError – If args are not valid.
Attributes
- analysis¶
Return the analysis instance for the experiment
- backend¶
Return the backend for the experiment
- experiment_options¶
Return the options for the experiment.
- experiment_type¶
Return experiment type.
- num_qubits¶
Return the number of qubits for the experiment.
- physical_qubits¶
Return the device qubits for the experiment.
Methods
- circuits()[source]¶
Returns the experiment’s circuits
- Return type:
List[QuantumCircuit]
- config()¶
Return the config dataclass for this experiment
- Return type:
- copy()¶
Return a copy of the experiment
- Return type:
- classmethod from_config(config)¶
Initialize an experiment from experiment config
- Return type:
- job_info(backend=None)¶
Get information about job distribution for the experiment on a specific backend.
- Parameters:
backend (Backend) – Optional, the backend for which to get job distribution information. If not specified, the experiment must already have a set backend.
- Returns:
A dictionary containing information about job distribution.
”Total number of circuits in the experiment”: Total number of circuits in the experiment.
”Maximum number of circuits per job”: Maximum number of circuits in one job based on backend and experiment settings.
”Total number of jobs”: Number of jobs needed to run this experiment on the currently set backend.
- Return type:
dict
- Raises:
QiskitError – if backend is not specified.
- run(backend=None, sampler=None, analysis='default', timeout=None, backend_run=None, **run_options)¶
Run an experiment and perform analysis.
- Parameters:
backend (Backend | None) – Optional, the backend to run on. Will override existing backend settings.
sampler (BaseSamplerV2 | None) – Optional, the sampler to run the experiment on. If None then a sampler will be invoked from previously set backend
analysis (BaseAnalysis | None) – Optional, a custom analysis instance to use for performing analysis. If None analysis will not be run. If
"default"
the experimentsanalysis()
instance will be used if it contains one.timeout (float | None) – Time to wait for experiment jobs to finish running before cancelling.
backend_run (bool | None) – Use backend run (temp option for testing)
run_options – backend runtime options used for circuit execution.
- Returns:
The experiment data object.
- Raises:
QiskitError – If experiment is run with an incompatible existing ExperimentData container.
- Return type:
- set_experiment_options(**fields)¶
Set the experiment options.
- Parameters:
fields – The fields to update the options
- Raises:
AttributeError – If the field passed in is not a supported options
- set_run_options(**fields)¶
Set options values for the experiment
run()
method.- Parameters:
fields – The fields to update the options
See also
The Setting options for your experiment guide for code example.
- set_transpile_options(**fields)¶
Set the transpiler options for
run()
method.- Parameters:
fields – The fields to update the options
- Raises:
QiskitError – If initial_layout is one of the fields.
See also
The Setting options for your experiment guide for code example.