中国物理学会期刊网
物理学报  2017, Vol.66 Issue (16): 160301  DOI:10.7498/aps.66.160301
有效质量法调控原子玻色-爱因斯坦凝聚体的双阱动力学
华东师范大学物理与材料科学学院, 上海 200062
Effective-mass approach to controlling double-well dynamics of atomic Bose-Einstein condensates
Department of Physics and Material Science, East China Normal University, Shanghai 200062, China

摘要

操控原子玻色-爱因斯坦凝聚体在双势阱中的动力学通常是通过改变势阱深度来实现,本文提出了一种基于调节原子有效质量的控制方案,可以在不改变双阱势的前提下操控凝聚体的双阱动力学.利用双模近似,本文解析地导出了超冷原子在双阱势中的隧穿强度和相互作用强度对有效质量的依赖关系,并基于平均场近似数值模拟了在有效质量调节下的凝聚体动力学演化,展示了隧穿振荡和自束缚等典型的双阱动力学行为.此外,本文的研究还发现,借助负有效质量效应,这一方案甚至可以等效地实现对负散射长度原子凝聚体双阱动力学行为的操控.

Abstract

The realization of Bose-Einstein condensation in dilute atomic gases opens an exciting way to quantum mechanics and begins a new area of quantum simulation. As a macroscopic quantum object and a many-body bosonic system, the Bose-Einstein condensates can show numerous exotic quantum effects and have naturally attracted great attention. One of the simplest quantum many-body systems to be realized experimentally and studied theoretically is ultra-cold atoms in a double-well potential. This system can exhibit a great variety of quantum interference phenomena such as tunneling oscillation, self-trapping and the entanglement of macroscopic superpositions. Specifically, the double-well potentials built by optical or magnetic fields are easy to change and the many-body interaction between ultra-cold atoms can be changed by the method of Feshbach resonance, enabling the precise quantum control of the double-well dynamics of the condensates.
In the present work, we study the dynamics of a condensate in a trapping potential consisting of an unalterable double-well trap and an additional moving optical lattice. If the lattice space is much smaller than the size of the double-well trap, the system can be simplified into a double-well trapped condensate with a tunable effective mass. Using the mean-field factorization assumption, together with a two-mode approximation, we obtain the analytic expressions for the dependence of the tunneling rate and the self-collision strength on the effective mass. The tunneling rate decays and the collision strength grows up with the increase of the effective mass. As a consequence of their different changes, we conclude that the adjustment of the effective mass of the ultra-cold atoms, rather than the changing of the trap barrier or adjusting of the atomic scattering length, is an alternative approach to controlling the double-well dynamics of the condensate. Via numerical simulations of the mean-field dynamical equations with some realistic parameters, we show that a transition between the quantum coherent tunneling and the self-trapping behaviors is experimentally realizable with the mass-control approach. Specifically, we show that the approach is still valid for the case of negative mass. Moreover, we find that the negative-mass case can be used even to stimulate the double-well dynamics of the condensate with a negative atomic scattering length.
收稿日期:2017-04-14

基金资助

国家自然科学基金(批准号:11574086,91436211,11234003)、国家重点研发计划(批准号:2016YFA0302001)、国家自然科学基金委应急管理项目(批准号:11654005)和上海市启明星人才计划(批准号:16QA1401600)资助的课题.
Project supported by the National Natural Science Foundation of China (Grant Nos. 11574086, 91436211, 11234003), the National Key Research and Development Program of China (Grant No. 2016YFA0302001), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 11654005), and the Shanghai Rising-Star Program, China (Grant No. 16QA1401600).

引用本文

[中文]
刘晓威, 张可烨. 有效质量法调控原子玻色-爱因斯坦凝聚体的双阱动力学[J]. 物理学报, 2017, 66(16): 160301.
[英文]
Liu Xiao-Wei, Zhang Ke-Ye. Effective-mass approach to controlling double-well dynamics of atomic Bose-Einstein condensates[J]. Acta Phys. Sin., 2017, 66(16): 160301.
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