Near-100 % two-photon-like coincidence-visibility dip with classical light and the role of complementarity

TL;DR

This paper demonstrates that classical light, with proper phase control, can produce a Hong-Ou-Mandel-like dip nearly 100%, challenging the notion that such dips are exclusive signatures of quantum light, and explores the role of complementarity.

Contribution

It shows that classical pulses can mimic quantum two-photon interference effects with near-perfect visibility, and clarifies the role of wave-particle complementarity in distinguishing quantum from classical light.

Findings

Classical microwave fields can produce a 99.635% coincidence dip.

Quantum states exhibit wave-particle complementarity, classical pulses do not.

Proper phase control enables classical light to mimic quantum interference effects.

Abstract

The Hong-Ou-Mandel effect is considered a signature of the quantumness of light, as the dip in coincidence probability using semi-classical theories has an upper bound of 50%. Here we show, theoretically and experimentally, that, with proper phase control of the signals, classical pulses can mimic a Hong-Ou-Mandel-like dip. We demonstrate a dip of 99.635 +/- 0.002% with classical microwave fields. Quantumness manifests in wave-particle complementarity of the two-photon state. We construct quantum and classical interferometers for the complementarity test and show that while the two-photon state shows wave-particle complementarity, the classical pulses do not.