Unified quantum density matrix description of coherence and polarization

TL;DR

This paper develops a unified quantum density matrix framework to describe and analyze the coherence and polarization of light, enabling better understanding of their evolution and decoherence in quantum optical systems.

Contribution

It introduces a quantum density matrix approach that combines coherence and polarization into a single theoretical framework, extending classical concepts into quantum optics.

Findings

Degree of polarization varies during free-space propagation.

Environmental interactions can suppress coherence and polarization.

Framework useful for analyzing decoherence in quantum information.

Abstract

The properties of coherence and polarization of light has been the subject of intense investigations and form the basis of many technological applications. These concepts which historically have been treated independently can now be formulated under a single classical theory. Here, we derive a quantum counterpart for this theory, with basis on a density matrix formulation, which describes jointly the coherence and polarization properties of an ensemble of photons. The method is used to show how the degree of polarization of a specific class of mixed states changes on propagation in free space, and how an interacting environment can suppress the coherence and polarization degrees of a general state. This last application can be particularly useful in the analysis of decoherence effects in optical quantum information implementations.