Ultrastrong linear optomechanical interaction

Abstract

Light-matter interaction in the ultrastrong coupling regime can be used to generate exotic ground states with two-mode squeezing and may be useful for quantum-enhanced sensing. Current demonstrations of ultrastrong coupling have been performed in fundamentally nonlinear systems. We report a cavity optomechanical system that operates in the linear coupling regime, reaching a maximum coupling of g_{x}/Ω_{x}=0.55±0.02. Such a system is inherently unstable, which may in the future enable strong mechanical squeezing.