Higher-order exceptional point in a blue-detuned non-Hermitian cavity optomechanical system

TL;DR

This paper proposes a non-Hermitian three-mode optomechanical system in the blue-detuned regime to realize and study third-order and second-order exceptional points, revealing new topological features and parameter tuning methods.

Contribution

It introduces a novel system setup for predicting higher-order exceptional points in blue-detuned non-Hermitian optomechanics, expanding understanding of EPs beyond red-detuned systems.

Findings

EP3 can be observed with neutral, gain, or loss mechanical resonators.

Multiple EP2s and EP3s can be predicted by tuning system parameters.

Distinct topological features of EPs are identified in the proposed system.

Abstract

Higher-order exceptional points (EPs) in non-Hermitian systems have attracted great interest due to their advantages in sensitive enhancement and distinct topological features. However, realization of such EPs is still challenged because more fine-tuning parameters is generically required in quantum systems, compared to the second-order EP (EP2). Here, we propose a non-Hermitian three-mode optomechanical system in the blue-sideband regime for predicting the third-order EP (EP3). By deriving the pseudo-Hermitian condition for the proposed system, one cavity with loss and the other one with gain must be required. Then we show EP3 or EP2 can be observed when the mechanical resonator (MR) is neutral, loss or gain. For the neutral MR, we find both two degenerate or two non-degenerate EP3s can be predicted by tuning system parameters in the parameter space, while four non-degenerate EP2s can be observed when the system parameters derivate from EP3s, which is distinguished from the previous study in the red-detuned optomechanical system. For the gain (loss) MR, we find only two degenerate EP3s or EP2s can be predicted by tuning enhanced coupling strength. Our proposal provides a potential way to predict higher-order EPs or multiple EP2s and study multimode quantum squeezing around EPs using the blue-detuned non-Hermitian optomechanical systems.