128 lines
5.4 KiB
Plaintext
128 lines
5.4 KiB
Plaintext
---
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title: EstimatorV2 (v0.35)
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description: API reference for qiskit_ibm_runtime.EstimatorV2 in qiskit-ibm-runtime v0.35
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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_ibm_runtime.EstimatorV2
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---
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# EstimatorV2
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<Class id="qiskit_ibm_runtime.EstimatorV2" isDedicatedPage={true} github="https://github.com/Qiskit/qiskit-ibm-runtime/tree/stable/0.35/qiskit_ibm_runtime/estimator.py#L44-L173" signature="EstimatorV2(mode=None, options=None)" modifiers="class">
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Bases: `BasePrimitiveV2`\[[`EstimatorOptions`](options-estimator-options "qiskit_ibm_runtime.options.estimator_options.EstimatorOptions")], `Estimator`, [`BaseEstimatorV2`](/api/qiskit/qiskit.primitives.BaseEstimatorV2 "(in Qiskit v1.3)")
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Class for interacting with Qiskit Runtime Estimator primitive service.
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Qiskit Runtime Estimator primitive service estimates expectation values of quantum circuits and observables.
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The [`run()`](#qiskit_ibm_runtime.EstimatorV2.run "qiskit_ibm_runtime.EstimatorV2.run") can be used to submit circuits, observables, and parameters to the Estimator primitive.
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Following construction, an estimator is used by calling its [`run()`](#qiskit_ibm_runtime.EstimatorV2.run "qiskit_ibm_runtime.EstimatorV2.run") method with a list of PUBs (Primitive Unified Blocs). Each PUB contains four values that, together, define a computation unit of work for the estimator to complete:
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* a single [`QuantumCircuit`](/api/qiskit/qiskit.circuit.QuantumCircuit "(in Qiskit v1.3)"), possibly parametrized, whose final state we define as $\psi(\theta)$,
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* one or more observables (specified as any `ObservablesArrayLike`, including `Pauli`, `SparsePauliOp`, `str`) that specify which expectation values to estimate, denoted $H_j$, and
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* a collection parameter value sets to bind the circuit against, $\theta_k$.
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* an optional target precision for expectation value estimates.
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Here is an example of how the estimator is used.
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```python
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from qiskit.circuit.library import RealAmplitudes
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from qiskit.quantum_info import SparsePauliOp
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from qiskit.transpiler.preset_passmanagers import generate_preset_pass_manager
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from qiskit_ibm_runtime import QiskitRuntimeService, EstimatorV2 as Estimator
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service = QiskitRuntimeService()
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backend = service.least_busy(operational=True, simulator=False)
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psi = RealAmplitudes(num_qubits=2, reps=2)
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hamiltonian = SparsePauliOp.from_list([("II", 1), ("IZ", 2), ("XI", 3)])
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theta = [0, 1, 1, 2, 3, 5]
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pm = generate_preset_pass_manager(backend=backend, optimization_level=1)
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isa_psi = pm.run(psi)
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isa_observables = hamiltonian.apply_layout(isa_psi.layout)
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estimator = Estimator(mode=backend)
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# calculate [ <psi(theta1)|hamiltonian|psi(theta)> ]
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job = estimator.run([(isa_psi, isa_observables, [theta])])
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pub_result = job.result()[0]
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print(f"Expectation values: {pub_result.data.evs}")
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```
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Initializes the Estimator primitive.
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**Parameters**
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* **mode** (*Optional\[Union\[BackendV1, BackendV2,* [*Session*](session "qiskit_ibm_runtime.Session")*,* [*Batch*](batch "qiskit_ibm_runtime.Batch")*, str]]*) –
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The execution mode used to make the primitive query. It can be:
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* A `Backend` if you are using job mode.
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* A [`Session`](session "qiskit_ibm_runtime.Session") if you are using session execution mode.
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* A [`Batch`](batch "qiskit_ibm_runtime.Batch") if you are using batch execution mode.
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Refer to the [Qiskit Runtime documentation](/guides/execution-modes). for more information about the `Execution modes`.
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* **options** (*Optional\[Union\[Dict,* [*EstimatorOptions*](options-estimator-options "qiskit_ibm_runtime.options.EstimatorOptions")*]]*) – Estimator options, see `EstimatorOptions` for detailed description.
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## Attributes
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### mode
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<Attribute id="qiskit_ibm_runtime.EstimatorV2.mode">
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Return the execution mode used by this primitive.
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**Returns**
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Mode used by this primitive, or `None` if an execution mode is not used.
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</Attribute>
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### options
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<Attribute id="qiskit_ibm_runtime.EstimatorV2.options">
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Return options
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</Attribute>
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### version
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<Attribute id="qiskit_ibm_runtime.EstimatorV2.version" attributeValue="2" />
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## Methods
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### backend
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<Function id="qiskit_ibm_runtime.EstimatorV2.backend" github="https://github.com/Qiskit/qiskit-ibm-runtime/tree/stable/0.35/qiskit_ibm_runtime/base_primitive.py#L221-L223" signature="backend()">
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Return the backend the primitive query will be run on.
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**Return type**
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BackendV1 | BackendV2
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</Function>
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### run
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<Function id="qiskit_ibm_runtime.EstimatorV2.run" github="https://github.com/Qiskit/qiskit-ibm-runtime/tree/stable/0.35/qiskit_ibm_runtime/estimator.py#L126-L149" signature="run(pubs, *, precision=None)">
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Submit a request to the estimator primitive.
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**Parameters**
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* **pubs** (*Iterable\[EstimatorPubLike]*) – An iterable of pub-like (primitive unified bloc) objects, such as tuples `(circuit, observables)` or `(circuit, observables, parameter_values)`.
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* **precision** (*float | 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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Submitted job.
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**Raises**
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**ValueError** – if precision value is not strictly greater than 0.
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**Return type**
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[RuntimeJobV2](runtime-job-v2 "qiskit_ibm_runtime.RuntimeJobV2")
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</Function>
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</Class>
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