Amplitude Amplification algorithm as a Gate in ops (#327)

* Amplitude Amplification algorithm as a Gate in ops * Amplitude Amplification algorithm as a Gate in ops, correct test_string_functions * Amplitude Amplification algorithm as a Gate in ops, correct coverage for _qaagate_test * Amplitude Amplification algorithm as a Gate in ops, correct test estimation statistics in phaseestimation_test * Try to triger Travis test because an apt get failure in the travis test * Address changes proposed by Damien * Address changes proposed by Damien, missed one * Address comments by Damien including eliminate the usage of algorith_inverse and eliminate QPE files form the PR * Address comments by Damien including eliminate the usage of algorith_inverse and eliminate QPE files form the PR, second try * Address comments by Damien forgot _qaagate_test * Update amplitudeamplification_test.py Wrap lines to 80 characters * Update amplitudeamplification.py Wrap lines to 80 characters * Update _qaagate.py Minor style correction * Update amplitudeamplification_test.py Cleanup imports
ProjectQ-Framework · Jul 18, 2019 · f3582b7 · f3582b7
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diff --git a/docs/projectq.ops.rst b/docs/projectq.ops.rst
@@ -55,6 +55,7 @@ The operations collection consists of various default gates and is a work-in-pro
 	projectq.ops.StatePreparation
 	projectq.ops.QPE
 	projectq.ops.FlipBits
+	projectq.ops.QAA
 
 
 Module contents

diff --git a/docs/projectq.setups.decompositions.rst b/docs/projectq.setups.decompositions.rst
@@ -27,6 +27,7 @@ The decomposition package is a collection of gate decomposition / replacement ru
     projectq.setups.decompositions.toffoli2cnotandtgate
     projectq.setups.decompositions.uniformlycontrolledr2cnot
     projectq.setups.decompositions.phaseestimation
+    projectq.setups.decompositions.amplitudeamplification
 
 
 Submodules
@@ -180,6 +181,13 @@ projectq.setups.decompositions.phaseestimation module
     :members:
     :undoc-members:
 
+projectq.setups.decompositions.amplitudeamplification module
+---------------------------------------------------------------
+
+.. automodule:: projectq.setups.decompositions.amplitudeamplification
+    :members:
+    :undoc-members:
+
 
 Module contents
 ---------------

diff --git a/projectq/ops/__init__.py b/projectq/ops/__init__.py
@@ -38,3 +38,4 @@
                                              UniformlyControlledRz)
 from ._state_prep import StatePreparation
 from ._qpegate import QPE
+from ._qaagate import QAA
diff --git a/projectq/ops/_qaagate.py b/projectq/ops/_qaagate.py
@@ -0,0 +1,81 @@
+#   Copyright 2019 ProjectQ-Framework (www.projectq.ch)
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+
+from ._basics import BasicGate
+
+
+class QAA(BasicGate):
+    """
+    Quantum Aplitude Aplification gate.
+
+    (Quick reference https://en.wikipedia.org/wiki/Amplitude_amplification.
+    Complete reference G. Brassard, P. Hoyer, M. Mosca, A. Tapp (2000)
+    Quantum Amplitude Amplification and Estimation
+    https://arxiv.org/abs/quant-ph/0005055)
+
+    Quantum Amplitude Amplification (QAA) executes the algorithm, but not
+    the final measurement required to obtain the marked state(s) with high
+    probability. The starting state on wich the QAA algorithm is executed
+    is the one resulting of aplying the Algorithm on the |0> state.
+
+    Example:
+        .. code-block:: python
+
+           def func_algorithm(eng,system_qubits):
+               All(H) | system_qubits
+
+           def func_oracle(eng,system_qubits,qaa_ancilla):
+               # This oracle selects the state |010> as the one marked
+               with Compute(eng):
+                  All(X) | system_qubits[0::2]
+               with Control(eng, system_qubits):
+                  X | qaa_ancilla
+               Uncompute(eng)
+
+           system_qubits = eng.allocate_qureg(3)
+           # Prepare the qaa_ancilla qubit in the |-> state
+           qaa_ancilla = eng.allocate_qubit()
+           X | qaa_ancilla
+           H | qaa_ancilla
+
+           # Creates the initial state form the Algorithm
+           func_algorithm(eng, system_qubits)
+           # Apply Quantum Amplitude Amplification the correct number of times
+           num_it = int(math.pi/4.*math.sqrt(1 << 3))
+           with Loop(eng, num_it):
+               QAA(func_algorithm, func_oracle) | (system_qubits, qaa_ancilla)
+
+           All(Measure) | system_qubits
+
+    Warning:
+        No qubit allocation/deallocation may take place during the call
+        to the defined Algorithm :code:`func_algorithm`
+
+    Attributes:
+        func_algorithm: Algorithm that initialite the state and to be used
+                        in the QAA algorithm
+        func_oracle: The Oracle that marks the state(s) as "good"
+        system_qubits: the system we are interested on
+        qaa_ancilla: auxiliary qubit that helps to invert the amplitude of the
+                     "good" states
+
+    """
+    def __init__(self, algorithm, oracle):
+        BasicGate.__init__(self)
+        self.algorithm = algorithm
+        self.oracle = oracle
+
+    def __str__(self):
+        return 'QAA(Algorithm = {0}, Oracle = {1})'.format(
+                str(self.algorithm.__name__), str(self.oracle.__name__))
diff --git a/projectq/ops/_qaagate_test.py b/projectq/ops/_qaagate_test.py
@@ -0,0 +1,27 @@
+#   Copyright 2019 ProjectQ-Framework (www.projectq.ch)
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+
+"""Tests for projectq.ops._qaagate."""
+
+from projectq.ops import _qaagate, All, H, X
+
+
+def test_qaa_str():
+
+    def func_algorithm(): All(H)
+
+    def func_oracle(): All(X)
+
+    gate = _qaagate.QAA(func_algorithm, func_oracle)
+    assert str(gate) == "QAA(Algorithm = func_algorithm, Oracle = func_oracle)"
diff --git a/projectq/setups/decompositions/__init__.py b/projectq/setups/decompositions/__init__.py
@@ -32,7 +32,8 @@
                toffoli2cnotandtgate,
                time_evolution,
                uniformlycontrolledr2cnot,
-               phaseestimation)
+               phaseestimation,
+               amplitudeamplification)
 
 all_defined_decomposition_rules = [
     rule
@@ -56,6 +57,7 @@
                    toffoli2cnotandtgate,
                    time_evolution,
                    uniformlycontrolledr2cnot,
-                   phaseestimation]
+                   phaseestimation,
+                   amplitudeamplification]
     for rule in module.all_defined_decomposition_rules
 ]
diff --git a/projectq/setups/decompositions/amplitudeamplification.py b/projectq/setups/decompositions/amplitudeamplification.py
@@ -0,0 +1,111 @@
+#   Copyright 2019 ProjectQ-Framework (www.projectq.ch)
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+"""
+Registers a decomposition for quantum amplitude amplification.
+
+(Quick reference https://en.wikipedia.org/wiki/Amplitude_amplification.
+Complete reference G. Brassard, P. Hoyer, M. Mosca, A. Tapp (2000)
+Quantum Amplitude Amplification and Estimation
+https://arxiv.org/abs/quant-ph/0005055)
+
+Quantum Amplitude Amplification (QAA) executes the algorithm, but not
+the final measurement required to obtain the marked state(s) with high
+probability. The starting state on wich the QAA algorithm is executed
+is the one resulting of aplying the Algorithm on the |0> state.
+
+Example:
+    .. code-block:: python
+
+       def func_algorithm(eng,system_qubits):
+           All(H) | system_qubits
+
+       def func_oracle(eng,system_qubits,qaa_ancilla):
+           # This oracle selects the state |010> as the one marked
+           with Compute(eng):
+              All(X) | system_qubits[0::2]
+           with Control(eng, system_qubits):
+              X | qaa_ancilla
+           Uncompute(eng)
+
+       system_qubits = eng.allocate_qureg(3)
+       # Prepare the qaa_ancilla qubit in the |-> state
+       qaa_ancilla = eng.allocate_qubit()
+       X | qaa_ancilla
+       H | qaa_ancilla
+
+       # Creates the initial state form the Algorithm
+       func_algorithm(eng, system_qubits)
+       # Apply Quantum Amplitude Amplification the correct number of times
+       num_it = int(math.pi/4.*math.sqrt(1 << 3))
+       with Loop(eng, num_it):
+         QAA(func_algorithm, func_oracle) | (system_qubits, qaa_ancilla)
+
+       All(Measure) | system_qubits
+
+Warning:
+    No qubit allocation/deallocation may take place during the call
+    to the defined Algorithm :code:`func_algorithm`
+
+Attributes:
+    func_algorithm: Algorithm that initialite the state and to be used
+                    in the QAA algorithm
+    func_oracle: The Oracle that marks the state(s) as "good"
+    system_qubits: the system we are interested on
+    qaa_ancilla: auxiliary qubit that helps to invert the amplitude of the
+                 "good" states
+
+"""
+
+import math
+import numpy as np
+
+from projectq.cengines import DecompositionRule
+from projectq.meta import Control, Compute, Uncompute, CustomUncompute, Dagger
+from projectq.ops import X, Z, Ph, All
+
+from projectq.ops import QAA
+
+
+def _decompose_QAA(cmd):
+    """ Decompose the Quantum Amplitude Apmplification algorithm as a gate. """
+    eng = cmd.engine
+
+    # System-qubit is the first qubit/qureg. Ancilla qubit is the second qubit
+    system_qubits = cmd.qubits[0]
+    qaa_ancilla = cmd.qubits[1]
+
+    # The Oracle and the Algorithm
+    Oracle = cmd.gate.oracle
+    A = cmd.gate.algorithm
+
+    # Apply the oracle to invert the amplitude of the good states, S_Chi
+    Oracle(eng, system_qubits, qaa_ancilla)
+
+    # Apply the inversion of the Algorithm,
+    # the inversion of the aplitude of |0> and the Algorithm
+
+    with Compute(eng):
+        with Dagger(eng):
+            A(eng, system_qubits)
+        All(X) | system_qubits
+    with Control(eng, system_qubits[0:-1]):
+        Z | system_qubits[-1]
+    with CustomUncompute(eng):
+        All(X) | system_qubits
+        A(eng, system_qubits)
+    Ph(math.pi) | system_qubits[0]
+
+
+#: Decomposition rules
+all_defined_decomposition_rules = [DecompositionRule(QAA, _decompose_QAA)]