Squeezed Ground States in a Spin-1 Bose-Einstein Condensate

We generate spin squeezed ground states in an atomic spin-1 Bose-Einstein condensate tuned nearthe quantum critical point between the polar and ferromagnetic quantum phases of the interactingspin ensemble. In contrast to typical non-equilibrium methods for preparing atomic squeezed statesby quenching through a quantum phase transition, squeezed ground states are time-stationary andremain squeezed for the lifetime of the condensate. A squeezed ground state with a metrologicalimprovement up to 6-8 dB and a constant squeezing angle maintained over 2 s is demonstrated.