text: # This code is part of Qiskit.
  #
  # (C) Copyright IBM 2017, 2019.
  #
  # 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.
  
  """Tests for Kraus quantum channel representation class."""
  
  import copy
  import unittest
  import numpy as np
  from numpy.testing import assert_allclose
  
  from qiskit import QiskitError
  from qiskit.quantum_info.states import DensityMatrix
  from qiskit.quantum_info import Kraus
  from .channel_test_case import ChannelTestCase
  
  
  class TestKraus(ChannelTestCase):
      """Tests for Kraus channel representation."""
  
      def test_init(self):
          """Test initialization"""
          # Initialize from unitary
          chan = Kraus(self.UI)
          assert_allclose(chan.data, [self.UI])
          self.assertEqual(chan.dim, (2, 2))
          self.assertEqual(chan.num_qubits, 1)
  
          # Initialize from Kraus
          chan = Kraus(self.depol_kraus(0.5))
          assert_allclose(chan.data, self.depol_kraus(0.5))
          self.assertEqual(chan.dim, (2, 2))
          self.assertEqual(chan.num_qubits, 1)
  
          # Initialize from Non-CPTP
          kraus_l, kraus_r = [self.UI, self.UX], [self.UY, self.UZ]
          chan = Kraus((kraus_l, kraus_r))
          assert_allclose(chan.data, (kraus_l, kraus_r))
          self.assertEqual(chan.dim, (2, 2))
          self.assertEqual(chan.num_qubits, 1)
  
          # Initialize with redundant second op
          chan = Kraus((kraus_l, kraus_l))
          assert_allclose(chan.data, kraus_l)
          self.assertEqual(chan.dim, (2, 2))
          self.assertEqual(chan.num_qubits, 1)
  
          # Initialize from rectangular
          kraus = [np.zeros((4, 2))]
          chan = Kraus(kraus)
          assert_allclose(chan.data, kraus)
          self.assertEqual(chan.dim, (2, 4))
          self.assertIsNone(chan.num_qubits)
  
          # Wrong input or output dims should raise exception
          self.assertRaises(QiskitError, Kraus, kraus, input_dims=4, output_dims=4)
  
      def test_circuit_init(self):
          """Test initialization from a circuit."""
          circuit, target = self.simple_circuit_no_measure()
          op = Kraus(circuit)
          target = Kraus(target)
          self.assertEqual(op, target)
  
      def test_circuit_init_except(self):
          """Test initialization from circuit with measure raises exception."""
          circuit = self.simple_circuit_with_measure()
          self.assertRaises(QiskitError, Kraus, circuit)
  
      def test_equal(self):
          """Test __eq__ method"""
          kraus = [self.rand_matrix(2, 2) for _ in range(2)]
          self.assertEqual(Kraus(kraus), Kraus(kraus))
  
      def test_copy(self):
          """Test copy method"""
          mat = np.eye(2)
          with self.subTest("Deep copy"):
              orig = Kraus(mat)
              cpy = orig.copy()
              cpy._data[0][0][0, 0] = 0.0
              self.assertFalse(cpy == orig)
          with self.subTest("Shallow copy"):
              orig = Kraus(mat)
              clone = copy.copy(orig)
              clone._data[0][0][0, 0] = 0.0
              self.assertTrue(clone == orig)
  
      def test_clone(self):
          """Test clone method"""
          mat = np.eye(4)
          orig = Kraus(mat)
          clone = copy.copy(orig)
          clone._data[0][0][0, 0] = 0.0
          self.assertTrue(clone == orig)
  
      def test_is_cptp(self):
          """Test is_cptp method."""
          self.assertTrue(Kraus(self.depol_kraus(0.5)).is_cptp())
          self.assertTrue(Kraus(self.UX).is_cptp())
          # Non-CPTP should return false
          self.assertFalse(Kraus(([self.UI], [self.UX])).is_cptp())
          self.assertFalse(Kraus([self.UI, self.UX]).is_cptp())
  
      def test_conjugate(self):
          """Test conjugate method."""
          kraus_l, kraus_r = self.rand_kraus(2, 4, 4), self.rand_kraus(2, 4, 4)
          # Single Kraus list
          targ = Kraus([np.conjugate(k) for k in kraus_l])
          chan1 = Kraus(kraus_l)
          chan = chan1.conjugate()
          self.assertEqual(chan, targ)
          self.assertEqual(chan.dim, (2, 4))
          # Double Kraus list
          targ = Kraus(([np.conjugate(k) for k in kraus_l], [np.conjugate(k) for k in kraus_r]))
          chan1 = Kraus((kraus_l, kraus_r))
          chan = chan1.conjugate()
          self.assertEqual(chan, targ)
          self.assertEqual(chan.dim, (2, 4))
  
      def test_transpose(self):
          """Test transpose method."""
          kraus_l, kraus_r = self.rand_kraus(2, 4, 4), self.rand_kraus(2, 4, 4)
          # Single Kraus list
          targ = Kraus([np.transpose(k) for k in kraus_l])
          chan1 = Kraus(kraus_l)
          chan = chan1.transpose()
          self.assertEqual(chan, targ)
          self.assertEqual(chan.dim, (4, 2))
          # Double Kraus list
          targ = Kraus(([np.transpose(k) for k in kraus_l], [np.transpose(k) for k in kraus_r]))
          chan1 = Kraus((kraus_l, kraus_r))
          chan = chan1.transpose()
          self.assertEqual(chan, targ)
          self.assertEqual(chan.dim, (4, 2))
  
      def test_adjoint(self):
          """Test adjoint method."""
          kraus_l, kraus_r = self.rand_kraus(2, 4, 4), self.rand_kraus(2, 4, 4)
          # Single Kraus list
          targ = Kraus([np.transpose(k).conj() for k in kraus_l])
          chan1 = Kraus(kraus_l)
          chan = chan1.adjoint()
          self.assertEqual(chan, targ)
          self.assertEqual(chan.dim, (4, 2))
          # Double Kraus list
          targ = Kraus(
              ([np.transpose(k).conj() for k in kraus_l], [np.transpose(k).conj() for k in kraus_r])
          )
          chan1 = Kraus((kraus_l, kraus_r))
          chan = chan1.adjoint()
          self.assertEqual(chan, targ)
          self.assertEqual(chan.dim, (4, 2))
  
      def test_compose_except(self):
          """Test compose different dimension exception"""
          self.assertRaises(QiskitError, Kraus(np.eye(2)).compose, Kraus(np.eye(4)))
          self.assertRaises(QiskitError, Kraus(np.eye(2)).compose, 2)
  
      def test_compose(self):
          """Test compose method."""
          # Random input test state
          rho = DensityMatrix(self.rand_rho(2))
  
          # UnitaryChannel evolution
          chan1 = Kraus(self.UX)
          chan2 = Kraus(self.UY)
          chan = chan1.compose(chan2)
          targ = rho & Kraus(self.UZ)
          self.assertEqual(rho & chan, targ)
  
          # 50% depolarizing channel
          chan1 = Kraus(self.depol_kraus(0.5))
          chan = chan1.compose(chan1)
          targ = rho & Kraus(self.depol_kraus(0.75))
          self.assertEqual(rho & chan, targ)
  
          # Compose different dimensions
          kraus1, kraus2 = self.rand_kraus(2, 4, 4), self.rand_kraus(4, 2, 4)
          chan1 = Kraus(kraus1)
          chan2 = Kraus(kraus2)
          targ = rho & chan1 & chan2
          chan = chan1.compose(chan2)
          self.assertEqual(chan.dim, (2, 2))
          self.assertEqual(rho & chan, targ)
          chan = chan1 & chan2
          self.assertEqual(chan.dim, (2, 2))
          self.assertEqual(rho & chan, targ)
  
      def test_dot(self):
          """Test dot method."""
          # Random input test state
          rho = DensityMatrix(self.rand_rho(2))
  
          # UnitaryChannel evolution
          chan1 = Kraus(self.UX)
          chan2 = Kraus(self.UY)
          targ = rho.evolve(Kraus(self.UZ))
          self.assertEqual(rho.evolve(chan1.dot(chan2)), targ)
  
          # 50% depolarizing channel
          chan1 = Kraus(self.depol_kraus(0.5))
          targ = rho & Kraus(self.depol_kraus(0.75))
          self.assertEqual(rho.evolve(chan1.dot(chan1)), targ)
  
          # Compose different dimensions
          kraus1, kraus2 = self.rand_kraus(2, 4, 4), self.rand_kraus(4, 2, 4)
          chan1 = Kraus(kraus1)
          chan2 = Kraus(kraus2)
          targ = rho & chan1 & chan2
          self.assertEqual(rho.evolve(chan2.dot(chan1)), targ)
  
      def test_compose_front(self):
          """Test deprecated front compose method."""
          # Random input test state
          rho = DensityMatrix(self.rand_rho(2))
  
          # UnitaryChannel evolution
          chan1 = Kraus(self.UX)
          chan2 = Kraus(self.UY)
          chan = chan1.compose(chan2, front=True)
          targ = rho & Kraus(self.UZ)
          self.assertEqual(rho & chan, targ)
  
          # 50% depolarizing channel
          chan1 = Kraus(self.depol_kraus(0.5))
          chan = chan1.compose(chan1, front=True)
          targ = rho & Kraus(self.depol_kraus(0.75))
          self.assertEqual(rho & chan, targ)
  
          # Compose different dimensions
          kraus1, kraus2 = self.rand_kraus(2, 4, 4), self.rand_kraus(4, 2, 4)
          chan1 = Kraus(kraus1)
          chan2 = Kraus(kraus2)
          targ = rho & chan1 & chan2
          chan = chan2.compose(chan1, front=True)
          self.assertEqual(chan.dim, (2, 2))
          self.assertEqual(rho & chan, targ)
  
      def test_expand(self):
          """Test expand method."""
          rho0, rho1 = np.diag([1, 0]), np.diag([0, 1])
          rho_init = DensityMatrix(np.kron(rho0, rho0))
          chan1 = Kraus(self.UI)
          chan2 = Kraus(self.UX)
  
          # X \otimes I
          chan = chan1.expand(chan2)
          rho_targ = DensityMatrix(np.kron(rho1, rho0))
          self.assertEqual(chan.dim, (4, 4))
          self.assertEqual(rho_init & chan, rho_targ)
  
          # I \otimes X
          chan = chan2.expand(chan1)
          rho_targ = DensityMatrix(np.kron(rho0, rho1))
          self.assertEqual(chan.dim, (4, 4))
          self.assertEqual(rho_init & chan, rho_targ)
  
          # Completely depolarizing
          chan_dep = Kraus(self.depol_kraus(1))
          chan = chan_dep.expand(chan_dep)
          rho_targ = DensityMatrix(np.diag([1, 1, 1, 1]) / 4)
          self.assertEqual(chan.dim, (4, 4))
          self.assertEqual(rho_init & chan, rho_targ)
  
      def test_tensor(self):
          """Test tensor method."""
          rho0, rho1 = np.diag([1, 0]), np.diag([0, 1])
          rho_init = DensityMatrix(np.kron(rho0, rho0))
          chan1 = Kraus(self.UI)
          chan2 = Kraus(self.UX)
  
          # X \otimes I
          chan = chan2.tensor(chan1)
          rho_targ = DensityMatrix(np.kron(rho1, rho0))
          self.assertEqual(chan.dim, (4, 4))
          self.assertEqual(rho_init & chan, rho_targ)
  
          # I \otimes X
          chan = chan1.tensor(chan2)
          rho_targ = DensityMatrix(np.kron(rho0, rho1))
          self.assertEqual(chan.dim, (4, 4))
          self.assertEqual(rho_init & chan, rho_targ)
  
          # Completely depolarizing
          chan_dep = Kraus(self.depol_kraus(1))
          chan = chan_dep.tensor(chan_dep)
          rho_targ = DensityMatrix(np.diag([1, 1, 1, 1]) / 4)
          self.assertEqual(chan.dim, (4, 4))
          self.assertEqual(rho_init & chan, rho_targ)
  
      def test_power(self):
          """Test power method."""
          # 10% depolarizing channel
          rho = DensityMatrix(np.diag([1, 0]))
          p_id = 0.9
          chan = Kraus(self.depol_kraus(1 - p_id))
  
          # Compose 3 times
          p_id3 = p_id ** 3
          chan3 = chan.power(3)
          targ3a = rho & chan & chan & chan
          self.assertEqual(rho & chan3, targ3a)
          targ3b = rho & Kraus(self.depol_kraus(1 - p_id3))
          self.assertEqual(rho & chan3, targ3b)
  
      def test_add(self):
          """Test add method."""
          # Random input test state
          rho = DensityMatrix(self.rand_rho(2))
          kraus1, kraus2 = self.rand_kraus(2, 4, 4), self.rand_kraus(2, 4, 4)
  
          # Random Single-Kraus maps
          chan1 = Kraus(kraus1)
          chan2 = Kraus(kraus2)
          targ = (rho & chan1) + (rho & chan2)
          chan = chan1._add(chan2)
          self.assertEqual(rho & chan, targ)
          chan = chan1 + chan2
          self.assertEqual(rho & chan, targ)
  
          # Random Single-Kraus maps
          chan = Kraus((kraus1, kraus2))
          targ = 2 * (rho & chan)
          chan = chan._add(chan)
          self.assertEqual(rho & chan, targ)
  
      def test_add_qargs(self):
          """Test add method with qargs."""
          rho = DensityMatrix(self.rand_rho(8))
          kraus = self.rand_kraus(8, 8, 4)
          kraus0 = self.rand_kraus(2, 2, 4)
  
          op = Kraus(kraus)
          op0 = Kraus(kraus0)
          eye = Kraus(self.UI)
  
          with self.subTest(msg="qargs=[0]"):
              value = op + op0([0])
              target = op + eye.tensor(eye).tensor(op0)
              self.assertEqual(rho & value, rho & target)
  
          with self.subTest(msg="qargs=[1]"):
              value = op + op0([1])
              target = op + eye.tensor(op0).tensor(eye)
              self.assertEqual(rho & value, rho & target)
  
          with self.subTest(msg="qargs=[2]"):
              value = op + op0([2])
              target = op + op0.tensor(eye).tensor(eye)
              self.assertEqual(rho & value, rho & target)
  
      def test_sub_qargs(self):
          """Test sub method with qargs."""
          rho = DensityMatrix(self.rand_rho(8))
          kraus = self.rand_kraus(8, 8, 4)
          kraus0 = self.rand_kraus(2, 2, 4)
  
          op = Kraus(kraus)
          op0 = Kraus(kraus0)
          eye = Kraus(self.UI)
  
          with self.subTest(msg="qargs=[0]"):
              value = op - op0([0])
              target = op - eye.tensor(eye).tensor(op0)
              self.assertEqual(rho & value, rho & target)
  
          with self.subTest(msg="qargs=[1]"):
              value = op - op0([1])
              target = op - eye.tensor(op0).tensor(eye)
              self.assertEqual(rho & value, rho & target)
  
          with self.subTest(msg="qargs=[2]"):
              value = op - op0([2])
              target = op - op0.tensor(eye).tensor(eye)
              self.assertEqual(rho & value, rho & target)
  
      def test_subtract(self):
          """Test subtract method."""
          # Random input test state
          rho = DensityMatrix(self.rand_rho(2))
          kraus1, kraus2 = self.rand_kraus(2, 4, 4), self.rand_kraus(2, 4, 4)
  
          # Random Single-Kraus maps
          chan1 = Kraus(kraus1)
          chan2 = Kraus(kraus2)
          targ = (rho & chan1) - (rho & chan2)
          chan = chan1 - chan2
          self.assertEqual(rho & chan, targ)
  
          # Random Single-Kraus maps
          chan = Kraus((kraus1, kraus2))
          targ = 0 * (rho & chan)
          chan = chan - chan
          self.assertEqual(rho & chan, targ)
  
      def test_multiply(self):
          """Test multiply method."""
          # Random initial state and Kraus ops
          rho = DensityMatrix(self.rand_rho(2))
          val = 0.5
          kraus1, kraus2 = self.rand_kraus(2, 4, 4), self.rand_kraus(2, 4, 4)
  
          # Single Kraus set
          chan1 = Kraus(kraus1)
          targ = val * (rho & chan1)
          chan = chan1._multiply(val)
          self.assertEqual(rho & chan, targ)
          chan = val * chan1
          self.assertEqual(rho & chan, targ)
  
          # Double Kraus set
          chan2 = Kraus((kraus1, kraus2))
          targ = val * (rho & chan2)
          chan = chan2._multiply(val)
          self.assertEqual(rho & chan, targ)
          chan = val * chan2
          self.assertEqual(rho & chan, targ)
  
      def test_multiply_except(self):
          """Test multiply method raises exceptions."""
          chan = Kraus(self.depol_kraus(1))
          self.assertRaises(QiskitError, chan._multiply, "s")
          self.assertRaises(QiskitError, chan.__rmul__, "s")
          self.assertRaises(QiskitError, chan._multiply, chan)
          self.assertRaises(QiskitError, chan.__rmul__, chan)
  
      def test_negate(self):
          """Test negate method"""
          rho = DensityMatrix(np.diag([1, 0]))
          targ = DensityMatrix(np.diag([-0.5, -0.5]))
          chan = -Kraus(self.depol_kraus(1))
          self.assertEqual(rho & chan, targ)
  
  
  if __name__ == "__main__":
      unittest.main()
  