Quantum dynamics of the phase of a Bose-Einstein condensate

Simsarian, Denschlag, Clark +6 more

Yafan Duan, Zhen Xu, Jun Qian +3 more

We numerically analyze the dynamic behavior of Bose—Einstein condensate (BEC) in a one-dimensional disordered potential before it completely loses spatial quantum coherence. We find that both the disorder statistics and the atom interactions produce remarkable effects on localization. We also find that the single phase of the initial condensate is broken into many small pieces while the system approaches localization, showing a counter-intuitive step-wise phase but not a thoroughly randomized phase. Although the condensates as a whole show less flow and expansion, the currents between adjacent phase steps retain strong time dependence. Thus we show explicitly that the localization of a finite size Bose—Einstein condensate is a dynamic equilibrium state.

J. Rogel-Salazar, G.H.C. New, Seok Jin Choi +1 more

Summary form only given. With the realisation of Bose-Einstein condensation in dilute gases, it has been possible to study the dynamics of quantum fields at finite temperatures. The Gross-Pitaevskii equation (GPE) has proved to be a very useful tool for describing Bose-Einstein condensates (BECs) and has shown very good agreement with experimental results at low temperatures. In the present paper we apply the mean-field approximation to describe the quantum state of a Bose-Einstein condensate, using a phase-space representation to visualise such a state.

Weidong Li, Xiaoji Zhou, Y.Q. Wang +2 more

King Lun Ng, Rodney Polkinghorne, Bogdan Opanchuk +1 more

Abstract Phase-space methods allow one to go beyond the mean-field approximation to simulate the quantum dynamics of interacting fields. Here, we obtain a technique for initializing either Wigner or positive-P phase-space simulations of Bose–Einstein condensates with quantum states at a finite temperature. As a means to calculate the initial states, we introduce the idea of a nonlinear chemical potential, which removes the zero-momentum phase-noise divergences of Bogoliubov theory to give a diagonal Hamiltonian. The resulting steady-state quantum theory is then directly applicable to the calculations of initial conditions for quantum simulations of BEC dynamics using phase-space techniques. These methods allow efficient and scalable simulation of large Bose–Einstein condensates. We suggest that nonlinear chemical potentials may have a general applicability to cases of broken symmetry.

Amichay Vardi, J. R. Anglin