Backscattering-immune optomechanical entanglement in a whispering-gallery-mode resonator

We propose how to achieve a backscattering-immune quantum system containing a cavity with defects. We find that, by placing a nanoparticle in the evanescent field of the whispering-gallery-mode resonator with proper relative position and size, the impact of backscattering induced by the defect can be almost eliminated completely. This makes it possible to realize backscattering immunity for both quantum entanglement and classical information transmission. We also show that both the degree of optomechanical entanglement and the transmissivity of the resonator can be manipulated by tuning the relative position of the nanoparticle. This work provides insights into the protection and manipulation of quantum and classical resources, which is meaningful for building noise-tolerant optomechanical quantum processors, achieving ideal quantum precision measurements and backscattering-immune integrated quantum photonic circuits.