Spin Squeezing through Collective Spin-Spin Interactions

Spin squeezing provides crucial quantum resource for quantum metrology and quantum information science. Here we propose that one axis-twisted (OAT) spin squeezing can be generated from free evolution under a general coupled-spin model with collective spin-spin interactions. We further propose pulse schemes to recover squeezing from parameter imperfections, and reach the extreme squeezing with Heisenberg-limited measurement precision scaling as $1\mathrm{/}N$ for $N$ particles. This work provides a feasible method for generating extreme spin squeezing.