124 lines
6.3 KiB
Plaintext
124 lines
6.3 KiB
Plaintext
---
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title: FasterAmplitudeEstimation
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description: API reference for qiskit.algorithms.FasterAmplitudeEstimation
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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.algorithms.FasterAmplitudeEstimation
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---
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# FasterAmplitudeEstimation
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<Class id="qiskit.algorithms.FasterAmplitudeEstimation" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.45/qiskit/algorithms/amplitude_estimators/fae.py" signature="qiskit.algorithms.FasterAmplitudeEstimation(delta, maxiter, rescale=True, quantum_instance=None, sampler=None)" modifiers="class">
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Bases: [`AmplitudeEstimator`](qiskit.algorithms.AmplitudeEstimator "qiskit.algorithms.amplitude_estimators.amplitude_estimator.AmplitudeEstimator")
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The Faster Amplitude Estimation algorithm.
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The Faster Amplitude Estimation (FAE) \[1] algorithm is a variant of Quantum Amplitude Estimation (QAE), where the Quantum Phase Estimation (QPE) by an iterative Grover search, similar to \[2].
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Due to the iterative version of the QPE, this algorithm does not require any additional qubits, as the originally proposed QAE \[3] and thus the resulting circuits are less complex.
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**References**
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**\[1]: K. Nakaji. Faster Amplitude Estimation, 2020;**
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[arXiv:2002.02417](https://arxiv.org/pdf/2003.02417.pdf)
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**\[2]: D. Grinko et al. Iterative Amplitude Estimation, 2019;**
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[arXiv:1912.05559](http://arxiv.org/abs/1912.05559)
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**\[3]: G. Brassard et al. Quantum Amplitude Amplification and Estimation, 2000;**
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[arXiv:quant-ph/0005055](http://arxiv.org/abs/quant-ph/0005055)
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<Admonition title="Deprecated since version 0.24.0" type="danger">
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`qiskit.algorithms.amplitude_estimators.fae.FasterAmplitudeEstimation.__init__()`’s argument `quantum_instance` is deprecated as of qiskit-terra 0.24.0. It will be removed no earlier than 3 months after the release date. Instead, use the `sampler` argument. See [https://qisk.it/algo\_migration](https://qisk.it/algo_migration) for a migration guide.
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</Admonition>
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**Parameters**
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* **delta** ([*float*](https://docs.python.org/3/library/functions.html#float "(in Python v3.12)")) – The probability that the true value is outside of the final confidence interval.
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* **maxiter** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.12)")) – The number of iterations, the maximal power of Q is 2 \*\* (maxiter - 1).
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* **rescale** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.12)")) – Whether to rescale the problem passed to estimate.
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* **quantum\_instance** ([*QuantumInstance*](qiskit.utils.QuantumInstance "qiskit.utils.QuantumInstance") *|*[*Backend*](qiskit.providers.Backend "qiskit.providers.Backend") *| None*) – Deprecated: The quantum instance or backend to run the circuits.
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* **sampler** ([*BaseSampler*](qiskit.primitives.BaseSampler "qiskit.primitives.BaseSampler") *| None*) – A sampler primitive to evaluate the circuits.
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<Admonition title="Note" type="note">
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This algorithm overwrites the number of shots set in the `quantum_instance` argument, but will reset them to the initial number after running.
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</Admonition>
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## Attributes
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### quantum\_instance
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<Attribute id="qiskit.algorithms.FasterAmplitudeEstimation.quantum_instance">
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Deprecated. Get the quantum instance.
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<Admonition title="Deprecated since version 0.24.0" type="danger">
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The property `qiskit.algorithms.amplitude_estimators.fae.FasterAmplitudeEstimation.quantum_instance` is deprecated as of qiskit-terra 0.24.0. It will be removed no earlier than 3 months after the release date. See [https://qisk.it/algo\_migration](https://qisk.it/algo_migration) for a migration guide.
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</Admonition>
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**Returns**
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The quantum instance used to run this algorithm.
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</Attribute>
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### sampler
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<Attribute id="qiskit.algorithms.FasterAmplitudeEstimation.sampler">
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Get the sampler primitive.
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**Returns**
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The sampler primitive to evaluate the circuits.
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</Attribute>
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## Methods
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### construct\_circuit
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<Function id="qiskit.algorithms.FasterAmplitudeEstimation.construct_circuit" signature="construct_circuit(estimation_problem, k, measurement=False)">
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Construct the circuit $Q^k X |0\rangle>$.
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The A operator is the unitary specifying the QAE problem and Q the associated Grover operator.
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**Parameters**
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* **estimation\_problem** ([*EstimationProblem*](qiskit.algorithms.EstimationProblem "qiskit.algorithms.EstimationProblem")) – The estimation problem for which to construct the circuit.
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* **k** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.12)")) – The power of the Q operator.
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* **measurement** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.12)")) – Boolean flag to indicate if measurements should be included in the circuits.
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**Returns**
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The circuit $Q^k X |0\rangle$.
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**Return type**
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[QuantumCircuit](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit") | [tuple](https://docs.python.org/3/library/stdtypes.html#tuple "(in Python v3.12)")\[[QuantumCircuit](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit"), [list](https://docs.python.org/3/library/stdtypes.html#list "(in Python v3.12)")\[[int](https://docs.python.org/3/library/functions.html#int "(in Python v3.12)")]]
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</Function>
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### estimate
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<Function id="qiskit.algorithms.FasterAmplitudeEstimation.estimate" signature="estimate(estimation_problem)">
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Run the amplitude estimation algorithm on provided estimation problem.
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**Parameters**
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**estimation\_problem** ([*EstimationProblem*](qiskit.algorithms.EstimationProblem "qiskit.algorithms.amplitude_estimators.estimation_problem.EstimationProblem")) – The estimation problem.
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**Returns**
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An amplitude estimation results object.
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**Raises**
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* [**ValueError**](https://docs.python.org/3/library/exceptions.html#ValueError "(in Python v3.12)") – A quantum instance or Sampler must be provided.
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* [**AlgorithmError**](algorithms#qiskit.algorithms.AlgorithmError "qiskit.algorithms.AlgorithmError") – Sampler run error.
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**Return type**
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[*FasterAmplitudeEstimationResult*](qiskit.algorithms.FasterAmplitudeEstimationResult "qiskit.algorithms.amplitude_estimators.fae.FasterAmplitudeEstimationResult")
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</Function>
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</Class>
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