Protecting Spin Squeezing with Square Noise

Here we provide two schemes to eliminate the square noise in the collective angular momentum during the generation of one-axis twisting (OAT) squeezed spin states (SSSs) by using the Radio frequency (RF) pulses. The first scheme can effectively overcome the detrimental noise and gives us a bare OAT Hamiltonian at last. The second one may also remove the noise well enough and finally offers us a two-axis twisting (TAT) Hamiltonian. In other words, it can both protect and enhance the OAT Hamiltonian. The corresponding theoretical analysis and numerical simulations are presented in the paper.