Optomechanical Dark Mode

TLDR

Thermal mechanical motion limits the use of mechanical systems in quantum applications, but a mechanically dark mode—an optical superposition decoupled from the oscillator—can still mediate effective optomechanical coupling. The study aims to use a mechanically dark mode to protect a system from mechanical dissipation instead of cooling the oscillator to its ground state. The authors realize the dark mode by weakly coupling two optical modes in a silica resonator to a single mechanical breathing mode. The dark mode enables optical field transfer between the two optical modes and suggests that mechanically mediated coupling can be employed in quantum applications without ground‑state cooling.

Abstract

Thermal mechanical motion hinders the use of a mechanical system in applications such as quantum information processing. Whereas the thermal motion can be overcome by cooling a mechanical oscillator to its motional ground state, an alternative approach is to exploit the use of a mechanically dark mode that can protect the system from mechanical dissipation. We have realized such a dark mode by coupling two optical modes in a silica resonator to one of its mechanical breathing modes in the regime of weak optomechanical coupling. The dark mode, which is a superposition of the two optical modes and is decoupled from the mechanical oscillator, can still mediate an effective optomechanical coupling between the two optical modes. We show that the formation of the dark mode enables the transfer of optical fields between the two optical modes. Optomechanical dark mode opens the possibility of using mechanically mediated coupling in quantum applications without cooling the mechanical oscillator to its motional ground state.