Quellcode für qiskit.circuit.library.boolean_logic.quantum_and

# This code is part of Qiskit.
# (C) Copyright IBM 2020.
# This code is licensed under the Apache License, Version 2.0. You may
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"""Implementations of boolean logic quantum circuits."""
from __future__ import annotations

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

[Doku]class AND(QuantumCircuit): r"""A circuit implementing the logical AND operation on a number of qubits. For the AND operation the state :math:`|1\rangle` is interpreted as ``True``. The result qubit is flipped, if the state of all variable qubits is ``True``. In this format, the AND operation equals a multi-controlled X gate, which is controlled on all variable qubits. Using a list of flags however, qubits can be skipped or negated. Practically, the flags allow to skip controls or to apply pre- and post-X gates to the negated qubits. The AND gate without special flags equals the multi-controlled-X gate: .. plot:: from qiskit.circuit.library import AND from qiskit.tools.jupyter.library import _generate_circuit_library_visualization circuit = AND(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`` and the last two are ``True`` we use the flags ``[-1, 0, 0, 1, 1]``. .. plot:: from qiskit.circuit.library import AND from qiskit.tools.jupyter.library import _generate_circuit_library_visualization circuit = AND(5, flags=[-1, 0, 0, 1, 1]) _generate_circuit_library_visualization(circuit) """ def __init__( self, num_variable_qubits: int, flags: list[int] | None = None, mcx_mode: str = "noancilla", ) -> None: """Create a new logical AND 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="and") # 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) 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="and") self.compose(circuit.to_gate(), qubits=self.qubits, inplace=True)