Emergence of multiphoton quantum coherence by light propagation

TL;DR

This paper demonstrates that linear propagation and scattering of thermal multiphoton wavepackets can modify their quantum coherence, leading to new quantum states with sub-shot-noise properties, impacting quantum technology applications.

Contribution

It reveals a novel phenomenon where free-space scattering alters quantum coherence of multiphoton systems, enabling the generation of nonclassical light with potential technological benefits.

Findings

Scattering modifies quantum coherence of multiphoton wavepackets.

Propagation can produce sub-shot-noise quantum states.

Validation through nonclassical van Cittert-Zernike theorem.

Abstract

The modification of the quantum properties of coherence of photons through their interaction with matter lies at the heart of the quantum theory of light. Indeed, the absorption and emission of photons by atoms can lead to different kinds of light with characteristic quantum statistical properties. As such, different types of light are typically associated with distinct sources. Here, we report on the observation of the modification of quantum coherence of multiphoton systems in free space. This surprising effect is produced by the scattering of thermal multiphoton wavepackets upon propagation. The modification of the excitation mode of a photonic system and its associated quantum fluctuations result in the formation of different light fields with distinct quantum coherence properties. Remarkably, we show that these processes of scattering can lead to multiphoton systems with sub-shot-noise quantum properties. Our observations are validated through the nonclassical formulation of the emblematic van Cittert-Zernike theorem. We believe that the possibility of producing quantum systems with modified properties of coherence, through linear propagation, can have dramatic implications for diverse quantum technologies.