qiskit.algorithms.FasterAmplitudeEstimation¶

class FasterAmplitudeEstimation(delta, maxiter, rescale=True, quantum_instance=None)[source]¶

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

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 (Union[Backend, BaseBackend, QuantumInstance, None]) – The quantum instance or backend to run 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.

__init__(delta, maxiter, rescale=True, quantum_instance=None)[source]¶

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 (Union[Backend, BaseBackend, QuantumInstance, None]) – The quantum instance or backend to run 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.

Methods

__init__(delta, maxiter[, rescale, …])

type delta: float

construct_circuit(estimation_problem, k[, …])

Construct the circuit \(Q^k X |0\rangle>\).

estimate(estimation_problem)

Run the amplitude estimation algorithm.

Attributes

quantum_instance

Get the quantum instance.

construct_circuit(estimation_problem, k, measurement=False)[source]¶

Construct the circuit \(Q^k X |0\rangle>\).

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.

Return type

Union[QuantumCircuit, Tuple[QuantumCircuit, List[int]]]

Returns

The circuit \(Q^k X |0\rangle\).

estimate(estimation_problem)[source]¶

Run the amplitude estimation algorithm.

Parameters: estimation_problem (EstimationProblem) – An EstimationProblem containing all problem-relevant information such as the state preparation and the objective qubits.
Return type: FasterAmplitudeEstimationResult

property quantum_instance¶

Get the quantum instance.

Return type: Optional[QuantumInstance]
Returns: The quantum instance used to run this algorithm.