Amplitude Estimation algorithms (#5517)

* ae codes

* add tests

* update docstrings in result objects

* add reno

* fix old aqua dependencies

* fix cyclic imports

* try fixing windows tests no. 1

* fix test

* try fixing windows attempt #2

* stefan's first comments

* accumulate -> evaluate in AE
* prob to meas 1 -> prob good state

* stefans comments pt. 2

* fix lint & indent

* add faster ae + bernoulli tests

* fix > 1 qubit case

* add comments

* add FAE specific tests

* raise error for rescale on custom q operator

* play with the oracles

* fix classicalregister > 1

* use correct reflection and rm X gates around oracle

* fix construction of rescaled est. problem

* fix phase in grover op

* adjust result objects

* adjust fae result object

* fix minus sign and lint

* rm trailing whitespaces

* fix tests

* fix lint

* rm utf8 header

* move rescale to problem, add evalschedule to MLAE

* code review suggestions

* state and obj.qubits not optional in estimation problem
* add QAE algos to documentation
* allow setting post processing and is good state to None to use default
* rm quantum instance logic from interface
* fix typehints for is good state
* add Faster AE to reno
* reset shots to user defined shots in FAE

* fix doc build (hopefully)

* add result classes to docs

* make grover op optional in setter

* rm reno -- there will be a global one

Co-authored-by: Matthew Treinish <mtreinish@kortar.org>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

qiskit/algorithms/__init__.py

@@ -48,6 +48,25 @@
    Grover
    GroverResult
 
+Amplitude Estimators
+++++++++++++++++++++
+
+.. autosummary::
+   :toctree: ../stubs/
+   :nosignatures:
+
+   AmplitudeEstimator
+   AmplitudeEstimatorResult
+   AmplitudeEstimation
+   AmplitudeEstimationResult
+   EstimationProblem
+   FasterAmplitudeEstimation
+   FasterAmplitudeEstimationResult
+   IterativeAmplitudeEstimation
+   IterativeAmplitudeEstimationResult
+   MaximumLikelihoodAmplitudeEstimation
+   MaximumLikelihoodAmplitudeEstimationResult
+
 Eigensolvers
 ++++++++++++
 Algorithms to find eigenvalues of an operator. For chemistry these can be used to find excited
@@ -109,6 +128,14 @@
 from .algorithm_result import AlgorithmResult
 from .variational_algorithm import VariationalAlgorithm, VariationalResult
 from .amplitude_amplifiers import Grover, GroverResult
+from .amplitude_estimators import (
+    AmplitudeEstimator, AmplitudeEstimatorResult,
+    AmplitudeEstimation, AmplitudeEstimationResult,
+    FasterAmplitudeEstimation, FasterAmplitudeEstimationResult,
+    IterativeAmplitudeEstimation, IterativeAmplitudeEstimationResult,
+    MaximumLikelihoodAmplitudeEstimation, MaximumLikelihoodAmplitudeEstimationResult,
+    EstimationProblem
+)
 from .eigen_solvers import NumPyEigensolver, Eigensolver, EigensolverResult
 from .factorizers import Shor, ShorResult
 from .minimum_eigen_solvers import (VQE, VQEResult, QAOA,
@@ -122,6 +149,17 @@
     'VariationalResult',
     'Grover',
     'GroverResult',
+    'AmplitudeEstimator',
+    'AmplitudeEstimatorResult',
+    'AmplitudeEstimation',
+    'AmplitudeEstimationResult',
+    'FasterAmplitudeEstimation',
+    'FasterAmplitudeEstimationResult',
+    'IterativeAmplitudeEstimation',
+    'IterativeAmplitudeEstimationResult',
+    'MaximumLikelihoodAmplitudeEstimation',
+    'MaximumLikelihoodAmplitudeEstimationResult',
+    'EstimationProblem',
     'NumPyEigensolver',
     'Eigensolver',
     'EigensolverResult',

qiskit/algorithms/amplitude_estimators/__init__.py

@@ -0,0 +1,34 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2020.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""The Amplitude Estimators package."""
+
+from .amplitude_estimator import AmplitudeEstimator, AmplitudeEstimatorResult
+from .ae import AmplitudeEstimation, AmplitudeEstimationResult
+from .fae import FasterAmplitudeEstimation, FasterAmplitudeEstimationResult
+from .iae import IterativeAmplitudeEstimation, IterativeAmplitudeEstimationResult
+from .mlae import MaximumLikelihoodAmplitudeEstimation, MaximumLikelihoodAmplitudeEstimationResult
+from .estimation_problem import EstimationProblem
+
+__all__ = [
+    'AmplitudeEstimator',
+    'AmplitudeEstimatorResult',
+    'AmplitudeEstimation',
+    'AmplitudeEstimationResult',
+    'FasterAmplitudeEstimation',
+    'FasterAmplitudeEstimationResult',
+    'IterativeAmplitudeEstimation',
+    'IterativeAmplitudeEstimationResult',
+    'MaximumLikelihoodAmplitudeEstimation',
+    'MaximumLikelihoodAmplitudeEstimationResult',
+    'EstimationProblem',
+]