text: from SimpleQmap import Qmap, StandardMap
  import matplotlib.pyplot as plt
  import numpy as np
  
  dim = 70
  k = 1.0
  qmin, qmax = 0.0, 1.0
  pmin, pmax = 0.0, 1.0
  domain = [[qmin,qmax],[pmin,pmax]]
  
  map = StandardMap(k=k)
  qmap = Qmap(map, dim, domain)
  
  evals, evecs = qmap.eigen() # get eigen value and eigen vectors
  
  print("is unitary?",np.all(np.abs(np.abs(evals*np.conj(evals))-np.ones(dim))<1e-12))
  
  
  fig = plt.figure(figsize=(6,6))
  theta = np.linspace(-np.pi,np.pi, 500)
  z = np.exp(-1.j*theta)
  plt.plot(evals.real, evals.imag, 'o',markersize=8)
  plt.plot(z.real, z.imag, '-k')
  plt.xlim(-1.1,1.1)
  plt.ylim(-1.1,1.1)
  plt.grid()
  plt.xlabel(r"$Re[u_n]$",fontsize=20)
  plt.ylabel(r"$Im[u_n]$",fontsize=20)
  plt.tight_layout()
  plt.savefig("eigen_values.png")
  plt.show()
  
  #for i, evec in enumerate(evecs):
  #    evec.savetxt("eigen_qrep_%i.dat" % i)
  
  