content: import numpy as np
  import scipy.linalg as la
  
  from qutip import spre, spost, qeye, sigmax, sigmay, sigmaz, qpt
  from qutip.core.gates import snot, cnot
  
  
  def test_qpt_snot():
      "quantum process tomography for snot gate"
  
      U_psi = snot()
      U_rho = spre(U_psi) * spost(U_psi.dag())
      N = 1
      op_basis = [[qeye(2), sigmax(), 1j * sigmay(), sigmaz()] for i in range(N)]
      # op_label = [["i", "x", "y", "z"] for i in range(N)]
      chi1 = qpt(U_rho, op_basis)
  
      chi2 = np.zeros((2 ** (2 * N), 2 ** (2 * N)), dtype=complex)
      chi2[1, 1] = chi2[1, 3] = chi2[3, 1] = chi2[3, 3] = 0.5
  
      assert (la.norm(chi2 - chi1) < 1e-8)
  
  
  def test_qpt_cnot():
      "quantum process tomography for cnot gate"
  
      U_psi = cnot()
      U_rho = spre(U_psi) * spost(U_psi.dag())
      N = 2
      op_basis = [[qeye(2), sigmax(), 1j * sigmay(), sigmaz()] for i in range(N)]
      # op_label = [["i", "x", "y", "z"] for i in range(N)]
      chi1 = qpt(U_rho, op_basis)
  
      chi2 = np.zeros((2 ** (2 * N), 2 ** (2 * N)), dtype=complex)
      chi2[0, 0] = chi2[0, 1] = chi2[1, 0] = chi2[1, 1] = 0.25
  
      chi2[12, 0] = chi2[12, 1] = 0.25
      chi2[13, 0] = chi2[13, 1] = -0.25
  
      chi2[0, 12] = chi2[1, 12] = 0.25
      chi2[0, 13] = chi2[1, 13] = -0.25
  
      chi2[12, 12] = chi2[13, 13] = 0.25
      chi2[13, 12] = chi2[12, 13] = -0.25
  
      assert (la.norm(chi2 - chi1) < 1e-8)
  