# Algorithms (qiskit.aqua.algorithms)¶

Aqua contains a collection of quantum algorithms, for use with quantum computers, to carry out research and investigate how to solve problems in different domains on near-term quantum devices with short depth circuits.

Algorithms configuration includes the use of components which were designed to be swappable sub-parts of an algorithm. Any component and may be exchanged for a different implementation of the same component type in order to potentially alter the behavior and outcome of the algorithm.

Quantum algorithms are run via a QuantumInstance which must be set with the desired backend where the algorithm’s circuits will be executed and be configured with a number of compile and runtime parameters controlling circuit compilation and execution. Aqua ultimately uses Terra for the actual compilation and execution of the quantum circuits created by the algorithm and its components.

# Algorithms Base Class¶

 QuantumAlgorithm Base class for Quantum Algorithms. ClassicalAlgorithm Base class for Classical Algorithms.

# Algorithms¶

Aqua contains a variety of quantum algorithms and these have been grouped by logical function such as minimum eigensolvers and amplitude amplifiers.

Additionally Aqua includes some classical algorithms. While these algorithms do not use a quantum device or simulator, and rely on purely classical approaches, they may be useful in the near term to generate reference values while experimenting with, developing and testing quantum algorithms.

The classical algorithms are designed to take the same input data as the quantum algorithms so that behavior, data validity and output can be evaluated and compared to a quantum result.

## Amplitude Amplifiers¶

 Grover Grover’s Search algorithm. GroverResult Grover Result.

## Amplitude Estimators¶

Algorithms that estimate a value.

 AmplitudeEstimationAlgorithmResult AmplitudeEstimationAlgorithm Result. AmplitudeEstimation The Quantum Phase Estimation-based Amplitude Estimation algorithm. AmplitudeEstimationResult AmplitudeEstimation Result. IterativeAmplitudeEstimation The Iterative Amplitude Estimation algorithm. IterativeAmplitudeEstimationResult IterativeAmplitudeEstimation Result. MaximumLikelihoodAmplitudeEstimation The Maximum Likelihood Amplitude Estimation algorithm. MaximumLikelihoodAmplitudeEstimationResult MaximumLikelihoodAmplitudeEstimation Result.

## Classifiers¶

Algorithms for data classification.

 QSVM Quantum SVM algorithm. VQC The Variational Quantum Classifier algorithm. SklearnSVM The Sklearn SVM algorithm (classical).

## Distribution Learners¶

 QGAN The Quantum Generative Adversarial Network algorithm.

## Education¶

Algorithms whose main role is educational. These are provided as Aqua algorithms so they can be run in the same framework but their existence here is principally for educational reasons.

 BernsteinVazirani The Bernstein-Vazirani algorithm. DeutschJozsa The Deutsch-Jozsa algorithm. EOH The Quantum EOH (Evolution of Hamiltonian) algorithm. Simon The Simon algorithm.

## Eigensolvers¶

Algorithms to find eigenvalues of an operator. For chemistry these can be used to find excited states of a molecule and qiskit.chemistry has some algorithms that leverage chemistry specific knowledge to do this in that application domain.

 Eigensolver The Eigensolver Interface. EigensolverResult Eigensolver Result.
 NumPyEigensolver The NumPy Eigensolver algorithm.

## Factorizers¶

Algorithms to find factors of a number.

 Shor Shor’s factoring algorithm.

## Linear Solvers¶

Algorithms to find solutions for linear equations of equations.

 LinearsolverResult Linear solver Result. HHL The HHL algorithm. HHLResult HHL Result. NumPyLSsolver The Numpy LinearSystem algorithm (classical). NumPyLSsolverResult Numpy LinearSystem Result.

## Minimum Eigensolvers¶

Algorithms that can find the minimum eigenvalue of an operator.

Note: The ClassicalCPLEX algorithm requires IBM ILOG CPLEX Optimization Studio and its Python API to be installed. See the following for more information:

 MinimumEigensolver The Minimum Eigensolver Interface. MinimumEigensolverResult Minimum Eigensolver Result.
 ClassicalCPLEX The Classical CPLEX algorithm (classical). IQPE The Iterative Quantum Phase Estimation algorithm. NumPyMinimumEigensolver The Numpy Minimum Eigensolver algorithm. QAOA The Quantum Approximate Optimization Algorithm. QPE The Quantum Phase Estimation algorithm. VQE The Variational Quantum Eigensolver algorithm.