text: # 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.
  
  # pylint: disable=no-member
  
  """XOR circuit."""
  
  from typing import Optional
  
  import numpy as np
  from qiskit.circuit import QuantumCircuit
  from qiskit.circuit.exceptions import CircuitError
  
  
  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:
              .. jupyter-execute::
                  :hide-code:
  
                  from qiskit.circuit.library import XOR
                  import qiskit.tools.jupyter
                  circuit = XOR(5, seed=42)
                  %circuit_library_info circuit
          """
          super().__init__(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:
                  self.x(i)
  