Counter-diabatic Spin Squeezing

Spin squeezing states (SSS) are atomic entangled states that can be used to enhance the atomic precision measurements beyond the standard quantum limit. Existing implementations relying on unitary evolution are primarily based on one-axis twisting induced through coherent cavity feedback. By adding an auxiliary driving Rabi field, our work can generalize this one-axis twisting to an equivalent two-axis twisting, which features robustness against technical imperfections, as well as the potential to reach higher squeezing and therefore greater metrological gain. Moreover, by optimizing the time-varying auxiliary field, we obtain a fast preparation of SSS with high metrological gain, which we call as counter-diabatic spin squeezing.