Source code for qiskit.circuit.library.boolean_logic.quantum_xor

# 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
# 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.

"""XOR circuit."""

from typing import Optional

import numpy as np
from qiskit.circuit import QuantumCircuit
from qiskit.circuit.exceptions import CircuitError

[docs]class XOR(QuantumCircuit): """An n_qubit circuit for bitwise xor-ing the input with some integer ``amount``. The ``amount`` is xor-ed in bitstring form with the input. This circuit can also represent addition by ``amount`` over the finite field GF(2). """ def __init__( self, num_qubits: int, amount: Optional[int] = None, seed: Optional[int] = None, ) -> None: """Return a circuit implementing bitwise xor. Args: num_qubits: the width of circuit. amount: the xor amount in decimal form. seed: random seed in case a random xor is requested. Raises: CircuitError: if the xor bitstring exceeds available qubits. Reference Circuit: .. plot:: from qiskit.circuit.library import XOR from import _generate_circuit_library_visualization circuit = XOR(5, seed=42) _generate_circuit_library_visualization(circuit) """ circuit = QuantumCircuit(num_qubits, name="xor") if amount is not None: if len(bin(amount)[2:]) > num_qubits: raise CircuitError("Bits in 'amount' exceed circuit width") else: rng = np.random.default_rng(seed) amount = rng.integers(0, 2**num_qubits) for i in range(num_qubits): bit = amount & 1 amount = amount >> 1 if bit == 1: circuit.x(i) super().__init__(*circuit.qregs, name="xor") self.compose(circuit.to_gate(), qubits=self.qubits, inplace=True)