A continuous-variable formalism for the Faraday atom-light interface

TL;DR

This paper introduces a continuous-variable formalism to analyze the quantum interface between polarized atomic ensembles and light, simplifying entanglement analysis and accommodating noisy, mixed states in experimental conditions.

Contribution

It develops a continuous-variable approach for matter-light interfaces, enabling analytical entanglement analysis and extension to mixed states with noise.

Findings

Analytical covariance matrix for entanglement characterization

Formalism applicable to noisy, mixed Gaussian states

Generation and analysis of multipartite cluster states

Abstract

Quantum interfaces between polarized atomic ensembles and coherent states of light, applied recently to manipulate bipartite and multipartite entanglement, are revisited by means of a continuous-variable formalism. The explicit use of the continuous-variable formalism facilitates significantly the analysis of entanglement between different modes, reducing it to the study of the properties of a final covariance matrix which can be found analytically. Furthermore, it allows to study matter-light interfaces for mixed states, adapting the formalism to the experimental situations in which the initial prepared Gaussian states are, unavoidably, affected by a certain amount of noise. A multipartite scenario, leading to the generation of macroscopic cluster states is presented and analyzed in detail within this formalism.