Long-Lived Squeezed Ground States in a Quantum Spin Ensemble

quantum-critical point separating the different spin phases of the interacting ensemble using a novel nonadiabatic technique. In contrast to typical nonequilibrium methods for preparing atomic squeezed states by quenching through a quantum phase transition, squeezed ground states are time stationary with a constant quadrature squeezing angle. A squeezed ground state with 6-8 dB of squeezing and a constant squeezing angle is demonstrated. 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.

Automated summary

This study successfully separates the quantum critical point between different interacting spin phases and achieves the preparation and measurement of squeezed ground states using a novel nonadiabatic technique. The experimental results show that the degree of squeezing in the squeezed ground state gradually decreases over time, which can be well modeled by the tuning of the Hamiltonian due to the loss of atomic density.