Swapping space for time: An alternative to time-domain interferometry

TL;DR

This paper introduces a novel quantum interference phenomenon where waves interfere over different times at a single slit, challenging traditional space-based interference concepts and offering an alternative to time-domain interferometry.

Contribution

It demonstrates a dual form of quantum interference occurring with a single slit at different times, expanding understanding of quantum wave behavior without time-dependent system modulation.

Findings

Counterintuitive interference increases with better path knowledge.

Formulas similar to Young's analysis derived from solvable models.

Potential prior observation in atomic interferometry misinterpreted as artifacts.

Abstract

Young's double-slit experiment requires two waves produced simultaneously at two different points in space. In quantum mechanics the waves correspond to a single quantum object, even as complex as a big molecule. An interference is present as long as one cannot tell for sure which slit is chosen by the object. The more we know about the path, the worse the interference. In the paper we show that quantum mechanics allows for a dual version of the phenomenon: self-interference of waves propagating through a single slit but at different moments of time. The effect occurs for time-independent Hamiltonians and thus should not be confused with Moshinsky-type time-domain interference, a consequence of active modulation of parameters of the system (oscillating mirrors, chopped beams, time-dependent apertures, moving gratings, etc.). The discussed phenomenon is counterintuitive even for those who are trained in quantum interferometry. For example, the more we know about the trajectory in space, the better the interference. Exactly solvable models lead to formulas deceptively similar to those from a Youngian analysis. There are reasons to believe that this new type of quantum interference was already observed in atomic interferometry almost three decades ago, but was misinterpreted and thus rejected as an artifact of unknown origin.