Source code for mqt.bench.benchmarks.dynamic_qft

# Copyright (c) 2023 - 2026 Chair for Design Automation, TUM
# Copyright (c) 2025 - 2026 Munich Quantum Software Company GmbH
# All rights reserved.
#
# SPDX-License-Identifier: MIT
#
# Licensed under the MIT License

"""Dynamic QFT benchmark definition."""

from __future__ import annotations

import numpy as np
from qiskit.circuit import ClassicalRegister, QuantumCircuit, QuantumRegister

from ._registry import register_benchmark




@register_benchmark("dynamic_qft", description="Dynamic Quantum Fourier Transformation (QFT)")
def create_circuit(num_qubits: int) -> QuantumCircuit:
    """Returns a quantum circuit implementing the Dynamic Quantum Fourier Transform algorithm.

    More details on the “Semiclassical Fourier Transform for Quantum Computation” can be found in https://arxiv.org/abs/quant-ph/9511007

    Arguments:
        num_qubits: number of qubits of the returned quantum circuit

    Returns:
        QuantumCircuit: a quantum circuit implementing the Dynamic Quantum Fourier Transform algorithm
    """
    q = QuantumRegister(num_qubits, "q")
    meas = ClassicalRegister(num_qubits, "meas")
    qc = QuantumCircuit(q, meas, name="dynamic_qft")

    # Mirror index order of regular "qft" benchmark
    for qubit in reversed(range(num_qubits)):
        for source in reversed(range(qubit + 1, num_qubits)):
            source_bit = num_qubits - source - 1
            with qc.if_test((meas[source_bit], 1)):
                qc.p(np.pi * (2.0 ** (qubit - source)), q[qubit])

        bit = num_qubits - qubit - 1
        qc.h(q[qubit])
        qc.measure(q[qubit], meas[bit])

    return qc