clifford_decompose_greedy.py

# This code is part of Qiskit.
#
# (C) Copyright IBM 2021, 2024.
#
# 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.
"""
Circuit synthesis for the Clifford class.
"""

# ---------------------------------------------------------------------
# Synthesis based on Bravyi et. al. greedy clifford compiler
# ---------------------------------------------------------------------

from qiskit.circuit import QuantumCircuit
from qiskit.quantum_info import Clifford

from qiskit._accelerate.synthesis.clifford import (
    synth_clifford_greedy as synth_clifford_greedy_inner,
)


def synth_clifford_greedy(clifford: Clifford) -> QuantumCircuit:
    """Decompose a :class:`.Clifford` operator into a :class:`.QuantumCircuit` based
    on the greedy Clifford compiler that is described in Appendix A of
    Bravyi, Hu, Maslov and Shaydulin [1].

    This method typically yields better CX cost compared to the Aaronson-Gottesman method.

    Note that this function only implements the greedy Clifford compiler from Appendix A
    of [1], and not the templates and symbolic Pauli gates optimizations
    that are mentioned in the same paper.

    Args:
        clifford: A Clifford operator.

    Returns:
        A circuit implementation of the Clifford.

    Raises:
        QiskitError: if symplectic Gaussian elimination fails.

    References:
        1. Sergey Bravyi, Shaohan Hu, Dmitri Maslov, Ruslan Shaydulin,
           *Clifford Circuit Optimization with Templates and Symbolic Pauli Gates*,
           `arXiv:2105.02291 [quant-ph] <https://arxiv.org/abs/2105.02291>`_
    """
    circuit = QuantumCircuit._from_circuit_data(
        synth_clifford_greedy_inner(clifford.tableau.astype(bool)), add_regs=True
    )
    circuit.name = str(clifford)
    return circuit