Quantum Coherence in Reflected and Refracted Beams: A Van Cittert-Zernike Approach

TL;DR

This paper introduces a quantum van Cittert-Zernike theorem to analyze how reflection and refraction at dielectric interfaces influence the quantum coherence and statistics of light beams, enabling controllable quantum state modifications without complex interactions.

Contribution

It develops a novel theoretical framework linking optical interface effects to quantum coherence evolution, revealing new methods for quantum state control and statistical manipulation.

Findings

Thermal light can exhibit sub-Poissonian statistics below shot noise.

Quantum coherence can be controlled via polarization coupling at interfaces.

A scaling law relates beam collimation to thermalization in quantum states.

Abstract

Recent advances in quantum optics have highlighted the critical role of spatial propagation in controlling the quantum coherence of light beams. However, the evolution of quantum coherence for light beams undergoing fundamental optical processes at dielectric interfaces remains unexplored. Furthermore, manipulating multiphoton correlations typically requires complex interactions that challenge few-photon level implementation. Here, we introduce a quantum van Cittert-Zernike theorem for light beams, describing how their coherence-polarization properties are influenced by reflection and refraction, as well as how these properties evolve upon subsequent propagation. Our work demonstrates that the quantum statistics of photonic systems can be controllably modified through the inherent polarization coupling arising from reflection and refraction at an interface, without relying on conventional light-matter interactions. Our approach reveals regimes where thermal light can exhibit sub-Poissonian statistics with fluctuations below the shot-noise level through post-selected measurements, and this statistical property can be tuned by the incident angle. Remarkably, this quantum statistical modification is governed by a scaling law linking beam collimation to far-field thermalization. Our work establishes a robust, decoherence-avoiding mechanism for quantum state control, advancing the fundamental understanding of coherence in quantum optics and opening new avenues for applications in quantum information and metrology.