Squeezed light in an optical parametric oscillator network with coherent feedback quantum control

TL;DR

This paper demonstrates how coherent quantum feedback in an optical parametric oscillator network can shape and broaden the squeezing spectrum of the output, enabling enhanced quantum control.

Contribution

It introduces a novel experimental setup using a quantum controller and feedback to engineer the squeezing spectrum of an OPO network.

Findings

Feedback shifts the maximum squeezing frequency.

Feedback broadens the squeezing spectrum.

Experimental results match theoretical predictions.

Abstract

We present squeezing and anti-squeezing spectra of the output from a degenerate optical parametric oscillator (OPO) network arranged in different coherent quantum feedback configurations. One OPO serves as a quantum plant, the other as a quantum controller. The addition of coherent feedback enables shaping of the output squeezing spectrum of the plant, and is found to be capable of pushing the frequency of maximum squeezing away from the optical driving frequency and broadening the spectrum over a wider frequency band. The experimental results are in excellent agreement with the developed theory, and illustrate the use of coherent quantum feedback to engineer the quantum-optical properties of the plant OPO output.