# -*- coding: utf-8 -*-
# This code is part of Qiskit.
#
# (C) Copyright IBM 2018, 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 Approximate IQFT."""
from qiskit.aqua.circuits import FourierTransformCircuits as ftc
from qiskit.aqua.utils.validation import validate_min
from . import IQFT
[docs]class Approximate(IQFT):
"""
The Approximate IQFT.
This form of IQFT generates the inverse of an Approximate Quantum Fourier Transform as
described in https://arxiv.org/abs/1803.04933.
"""
def __init__(self,
num_qubits: int,
degree: int = 0) -> None:
"""
Args:
num_qubits: The number of qubits
degree: The degree of approximation. 0 is the minimum value and causes no
approximation so will in fact be the same as a
:class:`~qiskit.aqua.components.iqfts.StandardIQFT`.
"""
validate_min('num_qubits', num_qubits, 1)
validate_min('degree', degree, 0)
super().__init__()
self._num_qubits = num_qubits
self._degree = degree
def _build_circuit(self, qubits=None, circuit=None, do_swaps=True):
return ftc.construct_circuit(
circuit=circuit,
qubits=qubits,
inverse=True,
approximation_degree=self._degree,
do_swaps=do_swaps
)
def _build_matrix(self):
raise NotImplementedError