text: # -*- coding: utf-8 -*-
  # pylint: disable=invalid-name
  
  # Copyright 2017 IBM RESEARCH. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  # =============================================================================
  
  """
  Element of SU(2).
  """
  from qiskit import CompositeGate
  from qiskit import Gate
  from qiskit import InstructionSet
  from qiskit import QuantumCircuit
  from qiskit import QuantumRegister
  from qiskit.extensions.standard import header  # pylint: disable=unused-import
  
  
  class UBase(Gate):
      """Element of SU(2)."""
  
      def __init__(self, theta, phi, lam, qubit, circ=None):
          super().__init__("U", [theta, phi, lam], [qubit], circ)
  
      def qasm(self):
          """Return OPENQASM string."""
          theta = self.param[0]
          phi = self.param[1]
          lamb = self.param[2]
          qubit = self.arg[0]
          return self._qasmif("U(%s,%s,%s) %s[%d];" % (
              theta, phi, lamb, qubit[0].name, qubit[1]))
  
      def inverse(self):
          """Invert this gate.
  
          U(theta,phi,lambda)^dagger = U(-theta,-lambda,-phi)
          """
          self.param[0] = -self.param[0]
          phi = self.param[1]
          self.param[1] = -self.param[2]
          self.param[2] = -phi
          return self
  
      def reapply(self, circ):
          """Reapply this gate to corresponding qubits in circ."""
          self._modifiers(circ.u_base(self.param[0], self.param[1], self.param[2],
                                      self.arg[0]))
  
  
  def u_base(self, theta, phi, lam, q):
      """Apply U to q."""
      if isinstance(q, QuantumRegister):
          gs = InstructionSet()
          for j in range(q.size):
              gs.add(self.u_base(theta, phi, lam, (q, j)))
          return gs
  
      self._check_qubit(q)
      return self._attach(UBase(theta, phi, lam, q, self))
  
  
  QuantumCircuit.u_base = u_base
  CompositeGate.u_base = u_base
  