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Source code for qiskit.circuit.library.data_preparation.zz_feature_map

# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 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.

"""Second-order Pauli-Z expansion circuit."""

from typing import Callable, List, Union, Optional
import numpy as np
from .pauli_feature_map import PauliFeatureMap


[docs]class ZZFeatureMap(PauliFeatureMap): """Second-order Pauli-Z evolution circuit. For 3 qubits and 1 repetition and linear entanglement the circuit is represented by: .. parsed-literal:: ┌───┐┌─────────────────┐ ┤ H ├┤ U1(2.0*φ(x[0])) ├──■────────────────────────────■──────────────────────────────────── ├───┤├─────────────────┤┌─┴─┐┌──────────────────────┐┌─┴─┐ ┤ H ├┤ U1(2.0*φ(x[1])) ├┤ X ├┤ U1(2.0*φ(x[0],x[1])) ├┤ X ├──■────────────────────────────■── ├───┤├─────────────────┤└───┘└──────────────────────┘└───┘┌─┴─┐┌──────────────────────┐┌─┴─┐ ┤ H ├┤ U1(2.0*φ(x[2])) ├──────────────────────────────────┤ X ├┤ U1(2.0*φ(x[1],x[2])) ├┤ X ├ └───┘└─────────────────┘ └───┘└──────────────────────┘└───┘ where ``φ`` is a classical non-linear function, which defaults to ``φ(x) = x`` if and ``φ(x,y) = (pi - x)(pi - y)``. Examples: >>> prep = ZZFeatureMap(2, reps=2) >>> print(prep) ┌───┐┌──────────────┐ q_0: ┤ H ├┤ U1(2.0*x[0]) ├──■───────────────────────────────────────■── ├───┤├──────────────┤┌─┴─┐┌─────────────────────────────────┐┌─┴─┐ q_1: ┤ H ├┤ U1(2.0*x[1]) ├┤ X ├┤ U1(2.0*(pi - x[0])*(pi - x[1])) ├┤ X ├ └───┘└──────────────┘└───┘└─────────────────────────────────┘└───┘ >>> from qiskit.circuit.library import EfficientSU2 >>> classifier = ZZFeatureMap(3) + EfficientSU2(3) >>> classifier.num_parameters 15 >>> classifier.parameters # 'x' for the data preparation, 'θ' for the SU2 parameters {Parameter(θ[9]), Parameter(θ[4]), Parameter(θ[6]), Parameter(θ[1]), Parameter(x[2]), Parameter(θ[7]), Parameter(x[1]), Parameter(θ[8]), Parameter(θ[2]), Parameter(θ[10]), Parameter(θ[5]), Parameter(θ[0]), Parameter(θ[3]), Parameter(x[0]), Parameter(θ[11])} >>> classifier.count_ops() OrderedDict([('u1', 12), ('cx', 12), ('ry', 12), ('cz', 9), ('h', 6)]) """
[docs] def __init__(self, feature_dimension: int, reps: int = 2, entanglement: Union[str, List[List[int]], Callable[[int], List[int]]] = 'full', data_map_func: Optional[Callable[[np.ndarray], float]] = None, insert_barriers: bool = False, ) -> None: """Create a new second-order Pauli-Z expansion. Args: feature_dimension: Number of features. reps: The number of repeated circuits, has a min. value of 1. entanglement: Specifies the entanglement structure. Refer to :class:`~qiskit.circuit.library.NLocal` for detail. data_map_func: A mapping function for data x. insert_barriers: If True, barriers are inserted in between the evolution instructions and hadamard layers. """ super().__init__(feature_dimension=feature_dimension, reps=reps, entanglement=entanglement, paulis=['Z', 'ZZ'], data_map_func=data_map_func, insert_barriers=insert_barriers)

© Copyright 2020, Qiskit Development Team. Last updated on 2021/03/04.

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