Double-slit experiment revisited

Abstract

The double-slit experiment is one of the quintessential quantum experiments. However, it tends to be overlooked that the build-up of the interference pattern involves single detection events with a random position and a random time of detection. Hence, a full theoretical account of this experiment requires the specification of the joint position and time distribution of detection at the screen, whose position marginal yields the famous interference pattern. The difficulty lies in what this distribution should be. While there are a variety of proposals for a quantum mechanical time observable , there is no consensus about the right choice. Here, we consider Bohmian mechanics, which allows for a natural and practical approach to this problem. We simulate this distribution in the case of an initial Gaussian wave packet passing through a double-slit potential. We also consider a more challenging setup in which one of the slits is closed during flight. To experimentally probe the quantum nature of the time distribution, a sufficient longitudinal spread of the initial wave packet is required, which has not been achieved so far. Without sufficient spread, the temporal aspect of the distribution can be treated classically. We illustrate this for the case of the double-slit experiment with helium atoms by Kurtsiefer et al. (1997), which reports the joint position and time distribution.