# Reversed interplay of quantum interference and which-way information in multi-photon entangled states

## TL;DR

This paper experimentally investigates multi-photon quantum interference in entangled states, revealing a non-monotonic relationship between distinguishability and interference, and suggests complex wave-particle duality phenomena in multi-particle systems.

## Contribution

It demonstrates the unusual resurgence of quantum interference with increased distinguishability in multi-photon entangled states, supported by theoretical analysis applicable to general Fock states.

## Key findings

- Interference signal reduces then resurges with increased distinguishability.
- Phenomenon occurs for any entangled Fock state of the form |N,M> + |M,N>.
- Results suggest complex wave-particle duality effects in multi-particle interference.

## Abstract

We report experimental studies of the multi-photon quantum interference of a two-mode three-photon entangled Fock state $|2, 1\rangle$ + $|1, 2\rangle$ impinging on a two-port balanced beam splitter. When the distinguishability between the two input paths is increased, we observe a reduction followed by a resurgence of the quantum interference signal. We ascribe this unusual behavior to the competition among contributions from distinct numbers of interfering photons. Our theoretical analysis shows that this phenomenon will occur for any entangled Fock-state input of the form $|N, M\rangle$ + $|M, N\rangle$ where M, N > 0. Our results are an indication that wave-particle duality may give rise to a wide range of, largely unexplored, phenomena in multi-particle interference.