.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/qaoa.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_gallery_qaoa.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_qaoa.py:


QAOA
====

Here we generate and optimize pattern for QAOA circuit.

.. GENERATED FROM PYTHON SOURCE LINES 10-31

.. code-block:: Python

    from __future__ import annotations

    import networkx as nx
    import numpy as np

    from graphix import Circuit

    rng = np.random.default_rng()

    n = 4
    xi: np.ndarray[tuple[int], np.dtype[np.float64]] = rng.random(6)
    theta: np.ndarray[tuple[int], np.dtype[np.float64]] = rng.random(4)
    g: nx.Graph[int] = nx.complete_graph(n)
    circuit = Circuit(n)
    for i, (u, v) in enumerate(g.edges):
        circuit.cnot(u, v)
        circuit.rz(v, xi[i])
        circuit.cnot(u, v)
    for v in g.nodes:
        circuit.rx(v, theta[v])








.. GENERATED FROM PYTHON SOURCE LINES 32-33

transpile and get the graph state

.. GENERATED FROM PYTHON SOURCE LINES 33-40

.. code-block:: Python


    pattern = circuit.transpile().pattern
    pattern.standardize()
    pattern.shift_signals()
    pattern.draw_graph(flow_from_pattern=False)





.. image-sg:: /gallery/images/sphx_glr_qaoa_001.png
   :alt: qaoa
   :srcset: /gallery/images/sphx_glr_qaoa_001.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    Pauli flow detected in the graph (causal flow not detected)




.. GENERATED FROM PYTHON SOURCE LINES 41-42

perform Pauli measurements and plot the new (minimal) graph to perform the same quantum computation

.. GENERATED FROM PYTHON SOURCE LINES 42-47

.. code-block:: Python


    pattern.remove_input_nodes()
    pattern.perform_pauli_measurements()
    pattern.draw_graph(flow_from_pattern=False)




.. image-sg:: /gallery/images/sphx_glr_qaoa_002.png
   :alt: qaoa
   :srcset: /gallery/images/sphx_glr_qaoa_002.png
   :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    Pauli flow detected in the graph (causal flow not detected)




.. GENERATED FROM PYTHON SOURCE LINES 48-49

finally, simulate the QAOA circuit

.. GENERATED FROM PYTHON SOURCE LINES 49-55

.. code-block:: Python


    out_state = pattern.simulate_pattern()
    state = circuit.simulate_statevector().statevec
    print("overlap of states: ", np.abs(np.dot(state.psi.flatten().conjugate(), out_state.psi.flatten())))
    # sphinx_gallery_thumbnail_number = 2





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    /home/docs/checkouts/readthedocs.org/user_builds/graphix/checkouts/v0.3.5/examples/qaoa.py:50: UserWarning: Default random-number generator is used. Results may not be reproducible.
      out_state = pattern.simulate_pattern()
    overlap of states:  0.9999999999999996





.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 1.114 seconds)


.. _sphx_glr_download_gallery_qaoa.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: qaoa.ipynb <qaoa.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: qaoa.py <qaoa.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: qaoa.zip <qaoa.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_