qfourier.py

#
# Copyright (c) 2019- Beit, Beit.Tech, Beit.Inc
#
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# furnished to do so, subject to the following conditions:
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# The above copyright notice and this permission notice shall be included in all
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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#

from math import pi
from typing import List

from quasar import All, H, If, Phase, Program, Qubit, Swap

#
##
#

def Fourier(
    qubits: List[Qubit]
) -> Program:
    prgm = Program()

    length = len(qubits)

    for i in range(length):
        prgm += H(qubits[i])

        for j in range(2, length + 1 - i):
            prgm += If(All(qubits[i + j - 1])).Then(
                Phase(qubits[i], 2 * pi / (2 ** j))
            )

    for i in range(length // 2):
        prgm += Swap(qubits[i], qubits[length - i - 1])

    return prgm