Multi-photon interference phenomena

TL;DR

This paper extends the understanding of multi-photon interference by demonstrating three- and four-photon interference phenomena, introducing a graph-theoretical framework, and exploring topological photonics with a photonic-crystal analogue of the Jackiw-Rossi model.

Contribution

It introduces a new framework for describing multi-photon interference and demonstrates complex interference effects even with distinguishable photons, advancing quantum optics and topological photonics.

Findings

Three-photon interference governed by four parameters

Strong quantum interference observed with highly distinguishable photons

Experimental realization of topological defect mode in photonic crystal

Abstract

In this work I demonstrate the interference of three photons, a generalisation of the famous Hong Ou Mandel (HOM) interference. I show that three-photon interference is governed by four parameters and measure three-photon interference independent of two-photon interference. I demonstrate that even when the states of the photons are highly distinguishable they can still exhibit strong quantum interference, challenging our intuition formed by the double slit and HOM interference. This is followed by a demonstration of four-photon interference, where surprisingly we can still observe a "fringe" when the involved particles are pairwise orthogonal. To explain these effects, I present a new framework to describe multi-photon interference in terms of a graph-theoretical approach, which illustrates the origin of different orders of multi-photon interference. My work leads to a more general definition of what we regard as an interference fringe in multi-photon scattering. This study of multi-photon interference is followed by an interdisciplinary work between photonics and solid state physics in the newly developing field of topological photonics. I realise a simulation of the Jackiw-Rossi model as a localised topological mode in a photonic-crystal analogue of the 2D graphene lattice. I succeed in the experimental demonstration of a single such excitation and I am able to study the detailed mode structure for the first time. The mode is a result of a topological defect and is, as such, protected against errors that do not change the topology of the system.