Fig. 1.
Phase problem for a 1D wave function. (A) Model 1D wave function of sinusoidal shape with wave number k0 and spatial extent L is Fourier transformed, yielding B. When taking the absolute value as in the measurement process (C) and subsequently transforming back to real space, the resulting real-space function D generally has the wrong phase and a spatial extent 2L, twice as large as the original wave function.