Observation of Dynamical Quantum Phase Transition in Antiferromagnetic Spinor Bose-Einstein Condensates in a short time region

In this work, we show direct evidence of the dynamical quantum phase transition(DQPT) in antiferromagnetic spin-1 Na Bose-Einstein condensate system. Initially, the spinor-1 BEC is at its ground state with quadratic Zeeman coeefficient q=11.2Hz where all atoms are in |F=1, m_F=0〉 state, i.e. the fraction of spin-0 atoms ρ₀ is 1, then at t=0, the q suddenly changed to a q_f and the BEC will evolve variable times at this q_f . To observe DQPT, first minimum dip depth (A_dip) of ρ₀(t) is choosen to be a new order parameter. The experimental result shows that once the final quadratice Zeeman coefficient q_f crossed the transiton point, ρ₀(t) will shows large fluctuation and A_dip will arise abruptly. Futher, the dip depths A_dip under different quenched parameters q_f shows similar behavior with the long time average ρ₀(t) which indicates the dynamical quantum phase transitions across the critical point.