Long-lived spin squeezed states in a Bose-Einstein condensate

We generate spin squeezed ground states in an atomic spin-1 Bose-Einstein condensate with 6–8 dB of squeezing and a constant squeezing angle. The long-term evolution of the squeezed ground state is measured and shows gradual decrease in the degree of squeezing over 2 s that is well modeled by a slow tuning of the Hamiltonian due to the loss of atomic density. Interestingly, modeling the gradual decrease does not require additional spin decoherence models despite a loss of 75% of the atoms.