C贸digo fuente para qiskit.circuit.library.boolean_logic.quantum_or

# 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.

"""Implementations of boolean logic quantum circuits."""
from __future__ import annotations
from typing import List, Optional

from qiskit.circuit import QuantumRegister, QuantumCircuit, AncillaRegister
from qiskit.circuit.library.standard_gates import MCXGate

[documentos]class OR(QuantumCircuit): r"""A circuit implementing the logical OR operation on a number of qubits. For the OR operation the state :math:`|1\rangle` is interpreted as ``True``. The result qubit is flipped, if the state of any variable qubit is ``True``. The OR is implemented using a multi-open-controlled X gate (i.e. flips if the state is :math:`|0\rangle`) and applying an X gate on the result qubit. Using a list of flags, qubits can be skipped or negated. The OR gate without special flags: .. plot:: from qiskit.circuit.library import OR from qiskit.tools.jupyter.library import _generate_circuit_library_visualization circuit = OR(5) _generate_circuit_library_visualization(circuit) Using flags we can negate qubits or skip them. For instance, if we have 5 qubits and want to return ``True`` if the first qubit is ``False`` or one of the last two are ``True`` we use the flags ``[-1, 0, 0, 1, 1]``. .. plot:: from qiskit.circuit.library import OR from qiskit.tools.jupyter.library import _generate_circuit_library_visualization circuit = OR(5, flags=[-1, 0, 0, 1, 1]) _generate_circuit_library_visualization(circuit) """ def __init__( self, num_variable_qubits: int, flags: Optional[List[int]] = None, mcx_mode: str = "noancilla", ) -> None: """Create a new logical OR circuit. Args: num_variable_qubits: The qubits of which the OR is computed. The result will be written into an additional result qubit. flags: A list of +1/0/-1 marking negations or omissions of qubits. mcx_mode: The mode to be used to implement the multi-controlled X gate. """ self.num_variable_qubits = num_variable_qubits self.flags = flags # add registers qr_variable = QuantumRegister(num_variable_qubits, name="variable") qr_result = QuantumRegister(1, name="result") circuit = QuantumCircuit(qr_variable, qr_result, name="or") # determine the control qubits: all that have a nonzero flag flags = flags or [1] * num_variable_qubits control_qubits = [q for q, flag in zip(qr_variable, flags) if flag != 0] # determine the qubits that need to be flipped (if a flag is > 0) flip_qubits = [q for q, flag in zip(qr_variable, flags) if flag > 0] # determine the number of ancillas num_ancillas = MCXGate.get_num_ancilla_qubits(len(control_qubits), mode=mcx_mode) if num_ancillas > 0: qr_ancilla = AncillaRegister(num_ancillas, "ancilla") circuit.add_register(qr_ancilla) else: qr_ancilla = AncillaRegister(0) circuit.x(qr_result) if len(flip_qubits) > 0: circuit.x(flip_qubits) circuit.mcx(control_qubits, qr_result[:], qr_ancilla[:], mode=mcx_mode) if len(flip_qubits) > 0: circuit.x(flip_qubits) super().__init__(*circuit.qregs, name="or") self.compose(circuit.to_gate(), qubits=self.qubits, inplace=True)