Enhancement of Field Squeezing Using Coherent Feedback

TL;DR

This paper demonstrates how coherent feedback can significantly enhance the squeezing of input quantum fields by an idealized degenerate parametric amplifier, analyzing spectral properties and in-loop effects.

Contribution

It introduces a simple feedback mechanism using a beam splitter to improve field squeezing in quantum feedback networks.

Findings

Enhanced squeezing achieved through feedback loop.

Spectral analysis reveals improved elastic and inelastic components.

Feedback mechanism increases the performance of quantum amplifiers.

Abstract

The theory of quantum feedback networks has recently been developed with the aim of showing how quantum input-output components may be connected together so as to control, stabilize or enhance the performance of one of the subcomponents. In this paper we show how the degree to which an idealized component (a degenerate parametric amplifier in the strong-coupling regime) can squeeze input fields may be enhanced by placing the component in-loop in a simple feedback mechanism involving a beam splitter. We study the spectral properties of output fields, placing particular emphasis on the elastic and inelastic components of the power density.