Experimental evidence for the physical delocalization of individual photons in an interferometer

TL;DR

This paper presents an experiment demonstrating that individual photons exhibit physical delocalization in an interferometer, with delocalization depending on the detection outcome, supporting the context-dependent nature of quantum reality.

Contribution

It provides direct experimental evidence for the physical delocalization of photons and its dependence on measurement context using polarization flip rates.

Findings

Photons in equal superpositions are delocalized in high probability output ports.

Photons are

super-localized

Abstract

It is generally assumed that the detection of a single photon as part of an interference pattern erases all possible which-path information. However, recent insights suggest that weak interactions can provide non-trivial experimental evidence for the physical delocalization of a single particle passing through an interferometer. Here, we present an experimental setup that can quantify the delocalization of individual photons using the rate of polarization flips induced by small rotations of polarization. The results show that photons detected in equal superpositions of the two paths are delocalized when detected in a high probability output port, and "super-localized" when detected in a low probability output port. We can thus confirm that delocalization depends on the detection of photons in the output of the interferometer, providing direct experimental evidence for the dependence of physical reality on the context established by a future measurement.