The trick of TEBD is to re-write the coefficients c i 1 i 2 . . i N : c i 1 i 2 . . i N = ∑ ∑ α α 1 , . . , α α N − − 1 = 0 χ χ Γ Γ α α 1 [ 1 ] i 1 λ λ α α 1 [ 1 ] Γ Γ α α 1 α α 2 [ 2 ] i 2 λ λ α α 2 [ 2 ] Γ Γ α α 2 α α 3 [ 3 ] i 3 λ λ α α 3 [ 3 ] ⋅ ⋅ . . ⋅ ⋅ Γ Γ α α N − − 2 α α N − − 1 [ N − − 1 ] i N − − 1 λ λ α α N − − 1 [ N − − 1 ] Γ Γ α α N − − 1 [ N ] i N