(a) and (e) Illustration of two-terminal and π-bar devices. The Anderson disorder exists only in the central (red) region. The size parameters are L_x = 120, W_x = 120, W_y = 60. (b)–(d) Two-terminal conductance G_12,12 of the device in panel (a); (f)–(h) nonlocal conductance G_14,23 of the device in panel (e) versus the Fermi energy ε_F for different disorder strengths W for the cases of a normal Z₂ = 0 system (b) and (f); Z₂ = 0 topological system with emergent robust helical edge states (c) and (g) and Z₂ = 1 QSHE (d) and (h). G_14,23 means that the current I₁₄ is injected from terminal 1 to 4 and the voltage V₂₃ is measured between terminals 2 and 3 and G_14,23 = V₂₃/I₁₄. The error bars denote the conductance fluctuation. Adapted from Ref. [33].