/
boolean_expression.py
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/
boolean_expression.py
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# This code is part of Qiskit.
#
# (C) Copyright IBM 2021.
#
# 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.
"""A quantum oracle constructed from a logical expression or a string in the DIMACS format."""
from os.path import basename, isfile
from typing import Callable, Optional
from qiskit.circuit import QuantumCircuit
from qiskit.utils.optionals import HAS_TWEEDLEDUM
from .classical_element import ClassicalElement
@HAS_TWEEDLEDUM.require_in_instance
class BooleanExpression(ClassicalElement):
"""The Boolean Expression gate."""
def __init__(self, expression: str, name: str = None, var_order: list = None) -> None:
"""
Args:
expression (str): The logical expression string.
name (str): Optional. Instruction gate name. Otherwise part of the expression is
going to be used.
var_order(list): A list with the order in which variables will be created.
(default: by appearance)
"""
from tweedledum import BoolFunction # pylint: disable=import-error
self._tweedledum_bool_expression = BoolFunction.from_expression(
expression, var_order=var_order
)
short_expr_for_name = (expression[:10] + "...") if len(expression) > 13 else expression
num_qubits = (
self._tweedledum_bool_expression.num_outputs()
+ self._tweedledum_bool_expression.num_inputs()
)
super().__init__(name or short_expr_for_name, num_qubits=num_qubits, params=[])
def simulate(self, bitstring: str) -> bool:
"""Evaluate the expression on a bitstring.
This evaluation is done classically.
Args:
bitstring: The bitstring for which to evaluate.
Returns:
bool: result of the evaluation.
"""
from tweedledum import BitVec # pylint: disable=import-error
bits = []
for bit in bitstring:
bits.append(BitVec(1, bit))
return bool(self._tweedledum_bool_expression.simulate(*bits))
def synth(
self,
registerless: bool = True,
synthesizer: Optional[Callable[["BooleanExpression"], QuantumCircuit]] = None,
):
"""Synthesis the logic network into a :class:`~qiskit.circuit.QuantumCircuit`.
Args:
registerless: Default ``True``. If ``False`` uses the parameter names
to create registers with those names. Otherwise, creates a circuit with a flat
quantum register.
synthesizer: A callable that takes self and returns a Tweedledum
circuit.
Returns:
QuantumCircuit: A circuit implementing the logic network.
"""
if registerless:
qregs = None
else:
qregs = None # TODO: Probably from self._tweedledum_bool_expression._signature
if synthesizer is None:
from .utils import tweedledum2qiskit # Avoid an import cycle
from tweedledum.synthesis import pkrm_synth # pylint: disable=import-error
truth_table = self._tweedledum_bool_expression.truth_table(output_bit=0)
return tweedledum2qiskit(pkrm_synth(truth_table), name=self.name, qregs=qregs)
return synthesizer(self)
def _define(self):
"""The definition of the boolean expression is its synthesis"""
self.definition = self.synth()
@classmethod
def from_dimacs_file(cls, filename: str):
"""Create a BooleanExpression from the string in the DIMACS format.
Args:
filename: A file in DIMACS format.
Returns:
BooleanExpression: A gate for the input string
Raises:
FileNotFoundError: If filename is not found.
"""
HAS_TWEEDLEDUM.require_now("BooleanExpression")
from tweedledum import BoolFunction # pylint: disable=import-error
expr_obj = cls.__new__(cls)
if not isfile(filename):
raise FileNotFoundError("The file %s does not exists." % filename)
expr_obj._tweedledum_bool_expression = BoolFunction.from_dimacs_file(filename)
num_qubits = (
expr_obj._tweedledum_bool_expression.num_inputs()
+ expr_obj._tweedledum_bool_expression.num_outputs()
)
super(BooleanExpression, expr_obj).__init__(
name=basename(filename), num_qubits=num_qubits, params=[]
)
return expr_obj