Correct me if I'm wrong, but isn't it a fact of quantum life that it's not possible to obtain a diffraction pattern from the double-slit, while at the same time knowing what photon emerged from what slit? And if I am not wrong, wouldn't it be a simple matter to conduct such an experiment based on Compton Scattering of certain X-rays to prove I'm not wrong? Consider a partition (opaque barrier) with the famous double slits etched into it. Then consider a three-dimensional medium of which the Compton X-rays fall upon after they come out of one slit or the other. This medium is a block of material (silver halide crystal substrate? Corning's PhotoGray silver halide glass blanks?) that will convert silver halide ---> silver under the irradiation of the X-ray. As the X-ray interacts with the silver halide molecule in the glass blank(?), it converts the halide and leaves behind a black streak of silver that can represent the direction the X-ray photon took. After the bombardment of the silver halide glass blank with the X-rays due to Compton Scattering, we should end up with many black streaks; half of which are lined up and pointing toward one slit, and the other half of which are lined up and pointing toward the other slit. The X-rays, now at a somewhat lower frequency due to Compton Scattering, will land on a detector screen where they will form the familiar diffraction pattern. Thus we have it: a three-dimentional medium that displays the photon paths in the form of unidimensional black streaks; each streak of which points to the slit each photon came from (contrary to QM); and, directly behind this medium, a screen displaying its diffraction pattern. Question: why wouldn't it work?