FasterAmplitudeEstimation

class qiskit.algorithms.FasterAmplitudeEstimation(delta, maxiter, rescale=True, quantum_instance=None, sampler=None)

Bases: AmplitudeEstimator

The Faster Amplitude Estimation algorithm.

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].

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.

References

[1]: K. Nakaji. Faster Amplitude Estimation, 2020;

arXiv:2002.02417

[2]: D. Grinko et al. Iterative Amplitude Estimation, 2019;

arXiv:1912.05559

[3]: G. Brassard et al. Quantum Amplitude Amplification and Estimation, 2000;

arXiv:quant-ph/0005055

Deprecated since version 0.24.0

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 for a migration guide.

Parameters

delta (float) – The probability that the true value is outside of the final confidence interval.
maxiter (int) – The number of iterations, the maximal power of Q is 2 ** (maxiter - 1).
rescale (bool) – Whether to rescale the problem passed to estimate.
quantum_instance (QuantumInstance |Backend | None) – Deprecated: The quantum instance or backend to run the circuits.
sampler (BaseSampler | None) – A sampler primitive to evaluate the circuits.

Note

This algorithm overwrites the number of shots set in the quantum_instance argument, but will reset them to the initial number after running.

Attributes

Deprecated. Get the quantum instance.

Deprecated since version 0.24.0

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 for a migration guide.

Returns

The quantum instance used to run this algorithm.

Get the sampler primitive.

Returns

The sampler primitive to evaluate the circuits.

construct_circuit(estimation_problem, k, measurement=False)

Q^k X |0\rangle>

The A operator is the unitary specifying the QAE problem and Q the associated Grover operator.

Parameters

estimation_problem (EstimationProblem) – The estimation problem for which to construct the circuit.
k (int) – The power of the Q operator.
measurement (bool) – Boolean flag to indicate if measurements should be included in the circuits.

Returns

Q^k X |0\rangle

Return type

QuantumCircuit | tuple [QuantumCircuit, list [int]]

estimate(estimation_problem)

Run the amplitude estimation algorithm on provided estimation problem.

Parameters

estimation_problem (EstimationProblem) - The estimation problem.

Returns

An amplitude estimation results object.

Raises

Return type

FasterAmplitudeEstimationResult

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