Decay of Loschmidt echo in a Bose-Einstein condensate at a dynamical phase transition.
We study the quantum Loschmidt echo (LE) in a Bose-Einstein condensate (BEC) in a double-well potential. The BEC may undergo a dynamical phase transition between two phases: a tunneling phase and a self-trapping phase. For sufficiently weak perturbation, the LE has Gaussian decay in both phases. While, for relatively strong perturbation, the LE has a Gaussian decay in the self-trapping phase and has a stretched exponential decay in the tunneling phase. This qualitative difference in the decaying law of the LE in the two phases provides a characterization of the dynamical phase transition of the BEC. The semiclassical theory is used to explain the numerically observed behaviors of the LE decay.
Zheng
Qiang
Q
Department of Physics, Nanjing University, Nanjing 210093, China.
Wang
Wen-ge
WG
Qin
Pinquan
P
Wang
Ping
P
Zhang
Xiaoping
X
Ren
Zhongzhou
Z