Obtaining tight bounds on higher-order interferences with a 5-path interferometer

TL;DR

This paper reports a high-precision optical experiment that sets the most stringent limits yet on the existence of higher-order interferences beyond standard quantum mechanics, reinforcing Born's rule.

Contribution

The study provides the tightest experimental bounds on higher-order interference terms, surpassing previous constraints by two orders of magnitude.

Findings

No detectable higher-order interference within experimental sensitivity.

Refined bounds on generalized interference theories.

Supports the validity of Born's rule in quantum mechanics.

Abstract

Within the established theoretical framework of quantum mechanics, interference always occurs between pairs of trajectories. Higher order interferences with multiple constituents are, however, excluded by Born's rule and can only exist in generalized probabilistic theories. Thus, high-precision experiments searching for such higher order interferences are a powerful method to distinguish between quantum mechanics and more general theories. Here, we perform such a test in optical multi-path interferometers. Our results rule out the existence of higher order interference terms to an extent which is more than four orders of magnitude smaller than the expected pairwise interference, refining previous bounds by two orders of magnitude. This establishes the hitherto tightest constraints on generalized interference theories.