title: Decay of Loschmidt echo in a Bose-Einstein condensate at a dynamical phase transition.
abstract: 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.
authors: Department of Physics, Nanjing University, Nanjing 210093, China.
authors: Qiang
authors: Q
authors: Zheng
authors: Wen-ge
authors: WG
authors: Wang
authors: Pinquan
authors: P
authors: Qin
authors: Ping
authors: P
authors: Wang
authors: Xiaoping
authors: X
authors: Zhang
authors: Zhongzhou
authors: Z
authors: Ren