Distinguishability and mixedness in quantum interference

TL;DR

This paper investigates how distinguishability and mixedness of quantum states affect multi-particle interference, revealing effects beyond two-particle interference and demonstrating their implications for quantum technologies.

Contribution

It experimentally demonstrates the influence of distinguishability and mixedness on three-photon interference, highlighting effects not observable in two-photon interference.

Findings

Three-photon interference differs for pure and mixed states with identical two-photon HOM interference.

Distinguishability and mixedness significantly impact multiphoton quantum interference.

Experimental results reveal new effects in quantum interference beyond traditional two-particle observations.

Abstract

We study the impact of distinguishability and mixedness -- two fundamental properties of quantum states -- on quantum interference. We show that these can influence the interference of multiple particles in different ways, leading to effects that cannot be observed in the interference of two particles alone. This is demonstrated experimentally by interfering three independent photons in pure and mixed states and observing their different multiphoton interference, despite exhibiting the same two-photon Hong-Ou-Mandel (HOM) interference. Besides its fundamental relevance, our observation has important implications for quantum technologies relying on photon interference.