What would one observe if instead of using a point source to illuminate the two slits a screen parallel to the two slits where portions of the screen are brighter and darker according to the relevant interference pattern, picture related.
If light at the screen is time-reversed and sent back toward the slits, the light will form two bright lines and pass back through the slits.
Exactly how to accomplish that is not necessarily obvious. However, the easiest way would be to record a hologram at the screen using the slits-diffracted light, then reconstruct the hologram using the reverse of whatever reference beam was used in recording the hologram. Recording and reconstructing the hologram this way ensures that the relative phase of the light at different places on the screen is properly accounted for.
Actually,the pattern on the screen constitutes a hologram in which light from the first slit can be considered to be the object beam and light from the second slit can be considered to be the reference beam. If the time-reverse of the light from the second slit is used to illuminate a photo of the pattern, diffraction from the pattern will send a portion of the illumination beam through the first slit.