Optomechanical systems offer unique opportunities to explore macroscopic quantum state and related
fundamental problems in quantum mechanics. Here, we propose a quantum optomechanical system
involving exchange interaction between spin angular momentum of light and a torsional oscillator. We
demonstrate that this system allows coherent control of the torsional quantum state of a torsional oscillator on the single-photon level, which facilitates efficient cooling and squeezing of the torsional oscillator.
Furthermore, the torsional oscillator with a macroscopic length scale can be prepared in Schrödinger catlike state. Our work provides a platform to verify the validity of quantum mechanics in macroscopic
systems on the micrometer and even centimeter scale.

Reference: Yuan Liu, Yaoming Chu, Shaoliang Zhang, and Jianming Cai, https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.17.054017