167 lines
6.8 KiB
Plaintext
167 lines
6.8 KiB
Plaintext
---
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title: BackendEstimator
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description: API reference for qiskit.primitives.BackendEstimator
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.primitives.BackendEstimator
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---
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# BackendEstimator
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<Class id="qiskit.primitives.BackendEstimator" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.24/qiskit/primitives/backend_estimator.py" signature="BackendEstimator(backend, options=None, abelian_grouping=True, bound_pass_manager=None, skip_transpilation=False)" modifiers="class">
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Bases: [`BaseEstimator`](qiskit.primitives.BaseEstimator "qiskit.primitives.base.base_estimator.BaseEstimator")\[`PrimitiveJob`\[[`EstimatorResult`](qiskit.primitives.EstimatorResult "qiskit.primitives.base.estimator_result.EstimatorResult")]]
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Evaluates expectation value using Pauli rotation gates.
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The [`BackendEstimator`](#qiskit.primitives.BackendEstimator "qiskit.primitives.BackendEstimator") class is a generic implementation of the [`BaseEstimator`](qiskit.primitives.BaseEstimator "qiskit.primitives.BaseEstimator") interface that is used to wrap a [`BackendV2`](qiskit.providers.BackendV2 "qiskit.providers.BackendV2") (or [`BackendV1`](qiskit.providers.BackendV1 "qiskit.providers.BackendV1")) object in the [`BaseEstimator`](qiskit.primitives.BaseEstimator "qiskit.primitives.BaseEstimator") API. It facilitates using backends that do not provide a native [`BaseEstimator`](qiskit.primitives.BaseEstimator "qiskit.primitives.BaseEstimator") implementation in places that work with [`BaseEstimator`](qiskit.primitives.BaseEstimator "qiskit.primitives.BaseEstimator"), such as algorithms in [`qiskit.algorithms`](algorithms#module-qiskit.algorithms "qiskit.algorithms") including [`VQE`](qiskit.algorithms.minimum_eigensolvers.VQE "qiskit.algorithms.minimum_eigensolvers.VQE"). However, if you’re using a provider that has a native implementation of [`BaseEstimator`](qiskit.primitives.BaseEstimator "qiskit.primitives.BaseEstimator"), it is a better choice to leverage that native implementation as it will likely include additional optimizations and be a more efficient implementation. The generic nature of this class precludes doing any provider- or backend-specific optimizations.
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Initalize a new BackendEstimator instance
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**Parameters**
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* **backend** – Required: the backend to run the primitive on
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* **options** – Default options.
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* **abelian\_grouping** – Whether the observable should be grouped into commuting
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* **bound\_pass\_manager** – An optional pass manager to run after parameter binding.
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* **skip\_transpilation** – If this is set to True the internal compilation of the input circuits is skipped and the circuit objects will be directly executed when this object is called.
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## Methods
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<span id="qiskit-primitives-backendestimator-run" />
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### run
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<Function id="qiskit.primitives.BackendEstimator.run" signature="BackendEstimator.run(circuits, observables, parameter_values=None, **run_options)">
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Run the job of the estimation of expectation value(s).
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`circuits`, `observables`, and `parameter_values` should have the same length. The i-th element of the result is the expectation of observable
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```python
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obs = observables[i]
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```
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for the state prepared by
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```python
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circ = circuits[i]
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```
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with bound parameters
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```python
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values = parameter_values[i].
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```
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**Parameters**
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* **circuits** (*Sequence\[*[*QuantumCircuit*](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")*] |* [*QuantumCircuit*](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")) – one or more circuit objects.
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* **observables** (*Sequence\[BaseOperator |* [*PauliSumOp*](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp") *| str] | BaseOperator |*[*PauliSumOp*](qiskit.opflow.primitive_ops.PauliSumOp "qiskit.opflow.primitive_ops.PauliSumOp") *| str*) – one or more observable objects. Several formats are allowed; importantly, `str` should follow the string representation format for [`Pauli`](qiskit.quantum_info.Pauli "qiskit.quantum_info.Pauli") objects.
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* **parameter\_values** (*Sequence\[Sequence\[float]] | Sequence\[float] | float | None*) – concrete parameters to be bound.
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* **run\_options** – runtime options used for circuit execution.
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**Returns**
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The job object of EstimatorResult.
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**Raises**
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* **TypeError** – Invalid argument type given.
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* **ValueError** – Invalid argument values given.
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**Return type**
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T
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</Function>
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<span id="qiskit-primitives-backendestimator-set-options" />
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### set\_options
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<Function id="qiskit.primitives.BackendEstimator.set_options" signature="BackendEstimator.set_options(**fields)">
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Set options values for the estimator.
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**Parameters**
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**\*\*fields** – The fields to update the options
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</Function>
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<span id="qiskit-primitives-backendestimator-set-transpile-options" />
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### set\_transpile\_options
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<Function id="qiskit.primitives.BackendEstimator.set_transpile_options" signature="BackendEstimator.set_transpile_options(**fields)">
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Set the transpiler options for transpiler. :param \*\*fields: The fields to update the options
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</Function>
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## Attributes
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### backend
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<Attribute id="qiskit.primitives.BackendEstimator.backend">
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Returns: The backend which this estimator object based on
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</Attribute>
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### circuits
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<Attribute id="qiskit.primitives.BackendEstimator.circuits">
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Quantum circuits that represents quantum states.
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**Returns**
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The quantum circuits.
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</Attribute>
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### observables
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<Attribute id="qiskit.primitives.BackendEstimator.observables">
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Observables to be estimated.
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**Returns**
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The observables.
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</Attribute>
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### options
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<Attribute id="qiskit.primitives.BackendEstimator.options">
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Return options values for the estimator.
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**Returns**
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options
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</Attribute>
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### parameters
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<Attribute id="qiskit.primitives.BackendEstimator.parameters">
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Parameters of the quantum circuits.
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**Returns**
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Parameters, where `parameters[i][j]` is the j-th parameter of the i-th circuit.
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</Attribute>
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### preprocessed\_circuits
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<Attribute id="qiskit.primitives.BackendEstimator.preprocessed_circuits">
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Transpiled quantum circuits produced by preprocessing :returns: List of the transpiled quantum circuit
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</Attribute>
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### transpile\_options
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<Attribute id="qiskit.primitives.BackendEstimator.transpile_options">
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Return the transpiler options for transpiling the circuits.
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</Attribute>
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### transpiled\_circuits
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<Attribute id="qiskit.primitives.BackendEstimator.transpiled_circuits">
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Transpiled quantum circuits. :returns: List of the transpiled quantum circuit
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**Raises**
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**QiskitError** – if the instance has been closed.
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</Attribute>
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</Class>
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