content: import numpy as np
  import matplotlib.pyplot as plt
  import qutip
  
  times = np.linspace(0, 10, 200)
  a = qutip.destroy(10)
  x = a.dag() + a
  H = a.dag() * a
  
  corr1 = qutip.correlation_2op_1t(H, None, times, [np.sqrt(0.5) * a], x, x)
  corr2 = qutip.correlation_2op_1t(H, None, times, [np.sqrt(1.0) * a], x, x)
  corr3 = qutip.correlation_2op_1t(H, None, times, [np.sqrt(2.0) * a], x, x)
  
  plt.plot(times, np.real(corr1), times, np.real(corr2), times, np.real(corr3))
  plt.xlabel(r'Time $t$')
  plt.ylabel(r'Correlation $\left<x(t)x(0)\right>$')
  plt.show()
  