Symmetry allows for distinguishability in totally destructive many-particle interference

TL;DR

This study demonstrates that in four-photon interference, symmetry rather than complete indistinguishability governs the suppression of certain output events, aligning with recent theoretical insights.

Contribution

It experimentally confirms that symmetry enables distinguishability in many-particle interference, challenging the assumption that total indistinguishability is necessary.

Findings

Suppression of output events depends on symmetric pairing, not mutual indistinguishability.

Experimental results match simulations accounting for realistic imperfections.

Symmetry controls interference patterns in complex multi-photon systems.

Abstract

We investigate, in a four photon interference experiment in a laser-written waveguide structure, how symmetries control the suppression of many-body output events of a $J_x$ unitary. We show that totally destructive interference does not require mutual indistinguishability between all, but only between symmetrically paired particles, in agreement with recent theoretical predictions. The outcome of the experiment is well described by a quantitative simulation which accounts for higher order emission of the photon source, imbalances in the scattering network, partial distinguishability, and photon loss.