# -*- coding: utf-8 -*-
# This code is part of Qiskit.
#
# (C) Copyright IBM 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.
""" Trotterization Algorithm Base """
import logging
from abc import abstractmethod
from ...operator_base import OperatorBase
from ..evolution_base import EvolutionBase
# TODO centralize handling of commuting groups
logger = logging.getLogger(__name__)
[docs]class TrotterizationBase(EvolutionBase):
""" A base for Trotterization methods, algorithms for approximating exponentiations of
operator sums by compositions of exponentiations.
"""
def __init__(self, reps: int = 1) -> None:
self._reps = reps
@property
def reps(self) -> int:
""" The number of repetitions to use in the Trotterization, improving the approximation
accuracy.
"""
return self._reps
@reps.setter
def reps(self, reps: int) -> None:
r""" Set the number of repetitions to use in the Trotterization. """
self._reps = reps
[docs] @abstractmethod
def convert(self, operator: OperatorBase) -> OperatorBase:
r"""
Convert a ``SummedOp`` into a ``ComposedOp`` or ``CircuitOp`` representing an
approximation of e^-i*``op_sum``.
Args:
operator: The ``SummedOp`` to evolve.
Returns:
The Operator approximating op_sum's evolution.
Raises:
TypeError: A non-SummedOps Operator is passed into ``convert``.
"""
raise NotImplementedError
# TODO @abstractmethod - trotter_error_bound