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animations_example.py

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+import qutip as qt
+import numpy as np
+import matplotlib.animation as animation
+import matplotlib.pyplot as plt
+from mpl_toolkits.mplot3d import Axes3D
+
+fig = plt.figure()
+ax = Axes3D(fig, azim=-40, elev=30)
+sphere = qt.Bloch(axes=ax)
+
+n_qbits = 8
+ts = 200
+T2 = 150
+
+sx = np.zeros((n_qbits, ts))
+sy = np.zeros((n_qbits, ts))
+sz = np.zeros((n_qbits, ts))
+
+w = 0.2*np.random.rand(n_qbits)
+
+for t in range(ts):
+    for i in range(n_qbits):
+        sx[i, t] = np.exp(-t/T2)*np.cos(w[i]*t)
+        # print(sx[i, t])
+        sy[i, t] = np.exp(-t/T2)*np.sin(w[i]*t)
+        sz[i, t] = 0
+
+
+def animate(i):
+    sphere.clear()
+    # sphere.add_vectors([[sx[i], sy[i], sz[i]], [sx[i], 0, 0]])
+    vec_tot = [0, 0, 0]
+    vec = []
+    for n in range(n_qbits):
+        vec.append([sx[n, i], sy[n, i], sz[n, i]])
+        vec_tot[0] += sx[n, i]
+        vec_tot[1] += sy[n, i]
+        vec_tot[2] += sz[n, i]
+    vec_tot[0] = vec_tot[0]/n_qbits
+    vec_tot[1] = vec_tot[1]/n_qbits
+    vec_tot[2] = vec_tot[2]/n_qbits
+    # print(vec)
+    sphere.vector_color = ['blueviolet']
+    sphere.vector_width = 2
+    sphere.add_vectors(vec)
+    sphere.vector_color = ['indigo']
+    sphere.vector_width = 7
+    sphere.add_vectors(vec_tot)
+    # sphere.add_points([sx[:i+1], sy[:i+1], sz[:i+1]])
+    sphere.make_sphere()
+    return ax
+
+
+def init():
+    sphere.zlabel = ["|0><0|", "|1><1|"]
+    sphere.point_size = [20]
+    sphere.point_color = ['blueviolet']
+    sphere.point_marker = ['o']
+    sphere.view = [-40, 30]
+
+    return ax
+
+
+ani = animation.FuncAnimation(fig, animate, np.arange(len(sx[0, :])),
+                              init_func=init, repeat=False)
+# ani.save('T2_with_proy.mp4', fps=20)
+ani.save('T2_multi.mp4', fps=20)