The Classical-to-Quantum Transition with Broadband Four-Wave Mixing

TL;DR

This paper investigates the transition from quantum to classical light in broadband four-wave mixing, covering an ultra-wide dynamic range and revealing quantum collapse and revival phenomena through two-photon interference.

Contribution

It introduces an experimental technique to observe the quantum-classical crossover over an 80dB photon flux range using two-photon interference in broadband FWM.

Findings

Observed quantum collapse and revival of interference.

Demonstrated the dependence of interference contrast on internal loss.

Mapped the quantum-to-classical transition across a large dynamic range.

Abstract

A key question of quantum optics is how nonclassical bi-photon correlations at low power evolve into classical coherence at high-power. Direct observation of the crossover from quantum to classical behavior is desirable, but difficult due to the lack of adequate experimental techniques that cover the ultra-wide dynamic range in photon flux from the single photon regime to the classical level. We investigate bi-photon correlations within the spectrum of light generated by broadband four-wave mixing (FWM) over a \emph{large dynamic range of $\sim80dB$ in photon flux} across the classical-to-quantum transition using a two-photon interference effect that distinguishes between classical and quantum behavior. We explore the quantum-classical nature of the light by observing the interference contrast dependence on internal loss and demonstrate quantum collapse and revival of the interference when the FWM gain in the fiber becomes imaginary.