Extreme spin squeezing: transforming non-squeezing interaction into squeezing interaction via rotation pulses

Spin squeezing plays an important role in quantum metrology and quantum information science. In realistic systems, the lack of required squeezing interactions prevents the generation of squeezing. We put forward a general scheme to synthesize extreme spin squeezing in non-squeezing systems. Aided with the periodical rotation pulses, we transform the original non-squeezing interaction into squeezing interaction, with significantly enhanced interaction strength. The sign of the enhanced interaction coefficient can also be altered, which can be applied to the time-reversal readout protocol for nonlinear interferometers. The obtained spin squeezing can ultimately reach the Heisenberg limit with measurement precision ∝ 1/N for N particles. Meanwhile, our scheme is demonstrated to be robust to fluctuations of pulse areas and pulse separations. This work provides the possibility of realizing extreme spin squeezing with Heisenberg-limited precision measurements in a large number of non-squeezing systems.