Input-output Gaussian channels: theory and application

TL;DR

This paper develops a theoretical framework for Gaussian quantum channels in open bosonic systems, applying it to quantum harmonic oscillators interacting with electromagnetic modes, revealing how squeezing and entanglement can be transferred and distributed.

Contribution

It introduces a novel formalism to characterize Gaussian channels relating initial correlations to output modes in open bosonic systems.

Findings

Quantifies squeezing transfer from intra-cavity oscillators to light.

Shows intra-cavity squeezing can be transformed into distributed optical entanglement.

Provides a framework applicable to systems like trapped ions and nanomechanical oscillators.

Abstract

Setting off from the classic input-output formalism, we develop a theoretical framework to characterise the Gaussian quantum channels relating the initial correlations of an open bosonic system to those of properly identified output modes. We then proceed to apply our formalism to the case of quantum harmonic oscillators, such as the motional degrees of freedom of trapped ions or nanomechanical oscillators, interacting with travelling electromagnetic modes through cavity fields and subject to external white noise. Thus, we determine the degree of squeezing that can be transferred from an intra-cavity oscillator to light, and also show that the intra-cavity squeezing can be transformed into distributed optical entanglement if one can access both output fields of a two-sided cavity.