A complete irreversible adiabatic transport of Bose-Einstein condensate (BEC) in a double-well trap is investigated within the mean field approximation. The transfer is driven by time-dependent (Gaussian) coupling between the wells and their relative detuning. The protocol successfully works in a wide range of both repulsive and attractive BEC interaction. The nonlinear effects caused by the interaction can be turned from detrimental into favorable for the transport. The results are compared with familiar Landau-Zener scenarios using the constant coupling. It is shown that the pulsed Gaussian coupling provides a new transport regime where coupling edges are decisive and convenient switch of the transport is possible.
Acceleration of adiabatic transport of interacting particles and rapid manipulations of dilute Bose gas in ground state
我们通过发展前面为单粒子系统形成的快进标度理论[Masuda和Nakamura，{ \it Proc. R. Soc.} A { \bf 466}，1135（2010）]。为了在任意短时间内获得最终绝热态，我们导出了一个驱动势，它可以加速全同粒子组成的量子系统的绝热动力学。利用快进标度理论，我们还展示了一个理想的快速操纵稀释玻色气体的基态无能量激发。
Using the time-dependent Bogoliubov approach, we study adiabaticity for a two-component Bose-Einstein condensate in a 3D time-dependent optical lattice with unit filling, in the superfluid and weakly interacting regime. We show that raising the lattice potential height can couple the ground state of the Bogoliubov Hamiltonian to excited states with two quasiparticles of opposite quasi-momenta. In the symmetric case for interactions and density in the two components these represent sound waves where the two components oscillate out of phase. We find an analytic expression of the adiabatic time,…
The variational theorem for the scattering length in the presence of the dipole-dipole interaction is developed. The theorem is applied to the spinless dipolar Bose gas in three dimensions. We calculated analytically the long-range tails of the single-particle momentum distribution and static structure factor, and the pair distribution function at short distances. The momentum distribution is inversely proportional to $q^4$ with the anisotropic prefactor. In the absence of the dipole-dipole interaction, Tan's adiabatic sweep theorem is reproduced as a particular case. For the homogeneous dilut…
We study the effect of interactions on the conversion of atomic -to molecular Bose-Einstein condensates via stimulated Raman adiabatic passage. Both energetic instability during avoided crossings and dynamical instability during chaotic intervals limit adiabaticity and impose {\em low} sweep-rate boundaries on the efficiency of the process. For the diabatic traverse of avoided crossings, we find a reciprocal power-law dependence of the final unconverted population on sweep rate. For the traverse of chaos, we find a sharp low-rate boundary determined by the dynamical instability parameters. The…
In this paper, the condensate fraction and the critical atom number and its corresponding critical temperature of condensate ultracold boson atoms trapped in optical box traps, are investigated. The semiclassical approximation is employed in this study. The boxes traps are modeled by a general power-law potential. The deviation of the boxes traps from an ideal boxes traps are discussed. The out come results furnish useful quantitative theoretical results for the future BEC experiments in such traps
We consider the 1d interacting Bose gas in the presence of time-dependent and spatially inhomogeneous contact interactions. Within its attractive phase, the gas allows for bound states of an arbitrary number of particles, which are eventually populated if the system is dynamically driven from the repulsive to the attractive regime. Building on the framework of Generalized Hydrodynamics, we analytically determine the formation of bound states in the limit of adiabatic changes in the interactions. Our results are valid for arbitrary initial thermal states and, more generally, Generalized Gibbs E…
We investigate spatial adiabatic passage of a Bose-Einstein condensate in a triple well potential within the three-mode approximation. By rewriting the dynamics in the so-called time-dependent dark/dressed basis, we analytically derive the optimal conditions for the non-linear parameter and the on-site energies of each well to achieve a highly efficient condensate transport. We show that the non-linearity yields a high-efficiency plateau for the condensate transport as a function of the on-site energy difference between the outermost wells, favoring the robustness of the transport. We also ana…
Robust stimulated Raman exact passages are requisite for controlling nonlinear quantum systems, with the wide applications ranging from ultracold molecules, non-linear optics to superchemistry. Inspired by shortcuts to adiabaticity, we propose the fast-forward scaling of stimulated Raman adiabatic processes with the nonlinearity involved, describing the transfer from an atomic Bose-Einstein condensate to a molecular one by controllable external fields. The fidelity and robustness of atom-molecule conversion are shown to surpass those of conventional adiabatic passages, assisted by fast-forward…
Shortcuts to adiabatic expansion of the effectively one-dimensional Bose-Einstein condensate (BEC) loaded in the harmonic-oscillator (HO) trap is investigated by combining techniques of the variational approximation and inverse engineering. Piecewise-constant (discontinuous) intermediate trap frequencies, similar to the known bang-bang forms in the optimal-control theory, are derived from an exact solution of a generalized Ermakov equation. Control schemes considered in the paper include imaginary trap frequencies at short time scales, i.e., the HO potential replaced by the quadratic repulsive…
A scheme is presented to perform an entangling gate between two atomic ensembles or Bose-Einstein condensates in a optical cavity with a common optical mode. The method involves using a generalized Stimulated Raman Adiabatic Passage (STIRAP) to adiabatically evolve the ground state. We show that dark states exist for any atom number within the cavities, and find that the operation produces an unusual type of evolution where the minimum of the number of atoms between two levels transitions to another state. This produces a unconventional type of entangling Hamiltonian which creates a phase depe…
In the present work, we develop an adiabatic invariant approach for the evolution of quasi-one-dimensional (stripe) solitons embedded in a two-dimensional Bose-Einstein condensate. The results of the theory are obtained both for the one-component case of dark soliton stripes, as well as for the considerably more involved case of the two-component dark-bright (alias "filled dark") soliton stripes. In both cases, analytical predictions regarding the stability and dynamics of these structures are obtained. One of our main findings is the determination of the instability modes of the waves as a fu…
Adiabatic preparation of a fractional quantum Hall fluid by coherently pumping atoms from a Bose-Einstein condensate
Pitaevskii BEC Center, INO-CNR and Dipartimento di Fisica, Università di Trento（皮塔耶夫斯基玻色-爱因斯坦凝聚中心，意大利国家研究委员会物质研究所和特伦托大学物理系）；Department of Physics, TU Dortmund University（多特蒙德大学物理系）；Technische Universität Berlin, Institut für Physik und Astronomie（柏林工业大学物理与天文学研究所）
