F=1 Spin-Nematic Squeezing Of A Spinor Bose-Einstein Condensate In An Optical Cavity

Spin-nematic squeezing of an F=1 spinor Bose-Einstein condensate(BEC)is a hot research topic in the field of quantum optics,also widely used in the field of precision measurement.The standard quantum limit(SQL)in measurement can be surpassed through squeezed states,which is of great significance for improving the precision of quantum interferometers.Especially in F=1 spinor BEC,there is a separatrix between the rotation region and the vibration region on a spinnematic sphere.As time evolves,the polar state at the saddle point will be squeezed along the separatrix with a fantastic squeezing effect.Based on this property,numerous research groups have proposed schemes to generate and increase spin-nematic squeezing.However,the studies above are all based on polar states,while our work focuses on a new scheme to obtain spin-nematic squeezing enhancement through spin-coherent states.We put an F=1 antiferromagnetic spinor BEC into an optical cavity driven by a coherent laser field to strengthen squeezing.The saddle point position and the separatrix can be tuned via cavity-pump detuning,second-order Zeeman shift,and light-atomic coupling strength.In this case,the saddle point corresponds to a spin-coherent state,instead of a polar state.Moreover,the spincoherent states at the saddle point,the separatrix,and the nearby regions are all squeezed almost along the separatrix,demonstrating an excellent squeezing effect and clear squeezing dynamics.Through tuning the detuning and the second-order Zeeman energy shift,the initial states with poor squeezing effects can be adjusted to the region near the separatrix,thus achieving the goal of squeezing enhancement.This research will have important research value in the field of precise measurement based on F=1 spinor Bose-Einstein condensates.