69 lines
4.9 KiB
Plaintext
69 lines
4.9 KiB
Plaintext
---
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title: BackendEstimatorV2
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description: API reference for qiskit.primitives.BackendEstimatorV2
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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.BackendEstimatorV2
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---
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# BackendEstimatorV2
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<Class id="qiskit.primitives.BackendEstimatorV2" isDedicatedPage={true} github="https://github.com/Qiskit/qiskit/tree/main/qiskit/primitives/backend_estimator_v2.py#L74-L390" signature="qiskit.primitives.BackendEstimatorV2(*, backend, options=None)" modifiers="class">
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Bases: [`BaseEstimatorV2`](qiskit.primitives.BaseEstimatorV2 "qiskit.primitives.base.base_estimator.BaseEstimatorV2")
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Evaluates expectation values for provided quantum circuit and observable combinations
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The [`BackendEstimatorV2`](#qiskit.primitives.BackendEstimatorV2 "qiskit.primitives.BackendEstimatorV2") class is a generic implementation of the [`BaseEstimatorV2`](qiskit.primitives.BaseEstimatorV2 "qiskit.primitives.BaseEstimatorV2") 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 [`BaseEstimatorV2`](qiskit.primitives.BaseEstimatorV2 "qiskit.primitives.BaseEstimatorV2") API. It facilitates using backends that do not provide a native [`BaseEstimatorV2`](qiskit.primitives.BaseEstimatorV2 "qiskit.primitives.BaseEstimatorV2") implementation in places that work with [`BaseEstimatorV2`](qiskit.primitives.BaseEstimatorV2 "qiskit.primitives.BaseEstimatorV2"). However, if you’re using a provider that has a native implementation of [`BaseEstimatorV2`](qiskit.primitives.BaseEstimatorV2 "qiskit.primitives.BaseEstimatorV2"), 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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This class does not perform any measurement or gate mitigation, and, presently, is only compatible with Pauli-based observables.
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Each tuple of `(circuit, observables, <optional> parameter values, <optional> precision)`, called an estimator primitive unified bloc (PUB), produces its own array-based result. The [`run()`](#qiskit.primitives.BackendEstimatorV2.run "qiskit.primitives.BackendEstimatorV2.run") method can be given a sequence of pubs to run in one call.
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The options for [`BackendEstimatorV2`](#qiskit.primitives.BackendEstimatorV2 "qiskit.primitives.BackendEstimatorV2") consist of the following items.
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* `default_precision`: The default precision to use if none are specified in [`run()`](#qiskit.primitives.BackendEstimatorV2.run "qiskit.primitives.BackendEstimatorV2.run"). Default: 0.015625 (1 / sqrt(4096)).
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* `abelian_grouping`: Whether the observables should be grouped into sets of qubit-wise commuting observables. Default: True.
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* `seed_simulator`: The seed to use in the simulator. If None, a random seed will be used. Default: None.
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**Parameters**
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* **backend** ([*BackendV1*](qiskit.providers.BackendV1 "qiskit.providers.BackendV1") *|*[*BackendV2*](qiskit.providers.BackendV2 "qiskit.providers.BackendV2")) – The backend to run the primitive on.
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* **options** ([*dict*](https://docs.python.org/3/library/stdtypes.html#dict "(in Python v3.12)") *| None*) – The options to control the default precision (`default_precision`), the operator grouping (`abelian_grouping`), and the random seed for the simulator (`seed_simulator`).
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## Attributes
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### backend
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<Attribute id="qiskit.primitives.BackendEstimatorV2.backend">
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Returns the backend which this sampler object based on.
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</Attribute>
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### options
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<Attribute id="qiskit.primitives.BackendEstimatorV2.options">
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Return the options
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</Attribute>
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## Methods
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### run
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<Function id="qiskit.primitives.BackendEstimatorV2.run" github="https://github.com/Qiskit/qiskit/tree/main/qiskit/primitives/backend_estimator_v2.py#L142-L151" signature="run(pubs, *, precision=None)">
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Estimate expectation values for each provided pub (Primitive Unified Bloc).
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**Parameters**
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* **pubs** (*Iterable\[EstimatorPubLike]*) – An iterable of pub-like objects, such as tuples `(circuit, observables)` or `(circuit, observables, parameter_values)`.
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* **precision** ([*float*](https://docs.python.org/3/library/functions.html#float "(in Python v3.12)") *| None*) – The target precision for expectation value estimates of each run Estimator Pub that does not specify its own precision. If None the estimator’s default precision value will be used.
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**Returns**
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A job object that contains results.
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**Return type**
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[PrimitiveJob](qiskit.primitives.PrimitiveJob "qiskit.primitives.PrimitiveJob")\[[PrimitiveResult](qiskit.primitives.PrimitiveResult "qiskit.primitives.PrimitiveResult")\[[PubResult](qiskit.primitives.PubResult "qiskit.primitives.PubResult")]]
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</Function>
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</Class>
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