Mesoscopic Interference with Fullerene Molecules

We analyze a double-slit experiment when the interfering particle is ``mesoscopic" (such as a fullerene molecule) and one endeavors to obtain Welcher Weg information by shining light on it. We derive a compact expression for the visibility of the interference pattern: coherence depends on both the spatial and temporal features of the wave function during its travel to the screen. We then focus on fullerene and set a bound on its temperature in order that its quantum mechanical coherence be maintained.