Entanglement and nonclassicality in four-mode Gaussian states generated via parametric down-conversion and frequency up-conversion

TL;DR

This paper investigates the generation and transfer of multipartite entanglement and nonclassicality in four-mode Gaussian states produced by simultaneous parametric down-conversion and frequency up-conversion, identifying conditions for high entanglement.

Contribution

It introduces conditions for generating highly entangled four-mode Gaussian states and demonstrates entanglement transfer between modes, providing new insights into nonclassical correlations.

Findings

Conditions for highly entangled states identified

Entanglement transfer between down- and up-converted modes suggested

Sub-shot-noise intensity correlations serve as entanglement indicators

Abstract

Multipartite entanglement and nonclassicality of four-mode Gaussian states generated in two simultaneous nonlinear processes involving parametric down-conversion and frequency up-conversion are analyzed assuming the vacuum as the initial state. Suitable conditions for the generation of highly entangled states are found. Transfer of the entanglement from the down-converted modes into the up-converted ones is also suggested. The analysis of the whole set of states reveals that sub-shot-noise intensity correlations between the equally-populated down-converted modes, as well as the equally-populated up-converted modes, uniquely identify entangled states. They represent a powerful entanglement identifier also in other cases with arbitrarily populated modes.