Quantum Coherent Nonlinear Feedbacks with Applications to Quantum Optics on Chip

TL;DR

This paper introduces a coherent feedback scheme to generate strong nonlinear quantum effects on chip, outperforming measurement-based feedback, with applications in quantum optics such as Kerr effect amplification and non-Gaussian light generation.

Contribution

It proposes a novel coherent feedback method for enhancing nonlinear quantum effects, enabling on-chip quantum optics applications that surpass traditional measurement-based approaches.

Findings

Nonlinear Kerr effect can be amplified to match linear effects in a TLR.

Non-Gaussian microwave light with sub-Poisson statistics can be generated.

The scheme enables strong nonlinear quantum optics on chip.

Abstract

In the control of classical mechanical systems, the feedback has been successfully applied to the production of the desired nonlinear dynamics. However, how much this can be done is still an open problem in quantum mechanical systems. This paper proposes a scheme of generating strong nonlinear quantum effects via the recently developed coherent feedback techniques, which can be shown to outperform the measurement-based quantum feedback scheme that can only generate pseudo-nonlinear quantum effects. Such advancement is demonstrated by two application examples in quantum optics on chip. In the first example, we show that the nonlinear Kerr effect can be generated and amplified to be comparable with the linear effect in a transmission line resonator (TLR). In the second example, we show that by tuning the gains of the quantum amplifiers in a TLR coherent feedback network, non-Gaussian "light" (microwave field) can be generated and manipulated via the nonlinear effects which exhibits fully quantum sub-Poisson photoncount statistics and photon antibunching phenomenon. The scheme opens promising applications in demonstrating strong nonlinear quantum optics on chip, which is extremely weak and inflexible in traditional quantum optical devices.