Source code for qurry.recipe.simple.cat

"""GHZ state (:mod:`qurry.recipe.simple.cat`)

The entangled circuit :class:`~qurry.recipe.simple.cat.GHZ`
as known as :class:`~qurry.recipe.simple.cat.Cat`,
which has been mentioned in the following reference.

Reference:
    -   Measurement of the Entanglement Spectrum of a Symmetry-Protected Topological State
        Using the IBM Quantum Computer - Choo, Kenny and von Keyserlingk, Curt W. and
        Regnault, Nicolas and Neupert, Titus
        `doi:10.1103/PhysRevLett.121.086808 <https://doi.org/10.1103/PhysRevLett.121.086808>`_

    .. code-block:: bibtex

        @article{PhysRevLett.121.086808,
            title = {
                Measurement of the Entanglement Spectrum of a Symmetry-Protected Topological State
                Using the IBM Quantum Computer},
            author = {
                Choo, Kenny and von Keyserlingk, Curt W. and Regnault, Nicolas and Neupert, Titus},
            journal = {Phys. Rev. Lett.},
            volume = {121},
            issue = {8},
            pages = {086808},
            numpages = {5},
            year = {2018},
            month = {Aug},
            publisher = {American Physical Society},
            doi = {10.1103/PhysRevLett.121.086808},
            url = {https://link.aps.org/doi/10.1103/PhysRevLett.121.086808}
        }

"""

from ..n_body import OneBody




class GHZ(OneBody):
    r"""The entangled circuit :class:`~qurry.recipe.simple.cat.GHZ`.

    .. code-block:: text

        # Open boundary at 8 qubits:
            ┌───┐
        q0: ┤ H ├──■────────────────────────────────
            └───┘┌─┴─┐
        q1: ─────┤ X ├──■───────────────────────────
                 └───┘┌─┴─┐
        q2: ──────────┤ X ├──■──────────────────────
                      └───┘┌─┴─┐
        q3: ───────────────┤ X ├──■─────────────────
                           └───┘┌─┴─┐
        q4: ────────────────────┤ X ├──■────────────
                                └───┘┌─┴─┐
        q5: ─────────────────────────┤ X ├──■───────
                                     └───┘┌─┴─┐
        q6: ──────────────────────────────┤ X ├──■──
                                          └───┘┌─┴─┐
        q7: ───────────────────────────────────┤ X ├
                                               └───┘

    .. math::

        \frac{1}{\sqrt{2}}
            \left({|01\rangle} - {|10\rangle} \right)^{\otimes N/2}, N = 8

    Args:
        num_qubits (int): The number of qubits for constructing the example circuit.
        name (str, optional): Name of case. Defaults to "ghz".
    """

    def __init__(self, num_qubits: int, name: str = "ghz") -> None:
        super().__init__(name=name)
        self.num_qubits = num_qubits

    def _build(self) -> None:
        if self._is_built:
            return
        super()._build()

        num_qubits = self.num_qubits
        if num_qubits == 0:
            return

        self.h(0)
        for i in range(1, num_qubits):
            self.cx(i - 1, i)





class Cat(GHZ):
    r""":class:`~qurry.recipe.simple.cat.Cat`,
    the anthor name of entangled circuit :class:`~qurry.recipe.simple.cat.GHZ`.

    .. code-block:: text

        # Open boundary at 8 qubits:
            ┌───┐
        q0: ┤ H ├──■────────────────────────────────
            └───┘┌─┴─┐
        q1: ─────┤ X ├──■───────────────────────────
                 └───┘┌─┴─┐
        q2: ──────────┤ X ├──■──────────────────────
                      └───┘┌─┴─┐
        q3: ───────────────┤ X ├──■─────────────────
                           └───┘┌─┴─┐
        q4: ────────────────────┤ X ├──■────────────
                                └───┘┌─┴─┐
        q5: ─────────────────────────┤ X ├──■───────
                                     └───┘┌─┴─┐
        q6: ──────────────────────────────┤ X ├──■──
                                          └───┘┌─┴─┐
        q7: ───────────────────────────────────┤ X ├
                                               └───┘

    .. math::

        \frac{1}{\sqrt{2}}
            \left({|01\rangle} - {|10\rangle} \right)^{\otimes N/2}, N = 8

    Args:
        num_qubits (int): The number of qubits for constructing the example circuit.
        name (str, optional): Name of case. Defaults to "cat".
    """

    def __init__(self, num_qubits: int, name: str = "cat") -> None:
        super().__init__(num_qubits=num_qubits, name=name)
        self.num_qubits = num_qubits