孤立波探索量子到经典的转变
Solitary waves explore the quantum-to-classical transition
AI总结：
本文提出在玻色-爱因斯坦凝聚体中通过明亮孤立波碰撞研究量子到经典转变，发现孤立波系综先失去相位相干性再产生纠缠，并基于五次平均场方程的相空间解释了这一退相干先行的必要性。
摘要：
我们的环境如何从底层的量子多体理论中呈现出经典外观，是一个悬而未决的基本问题。我们提出，量子到经典转变所涉及的现象可以在玻色-爱因斯坦凝聚体中明亮孤立波的碰撞中进行探测，在超冷温度下，数千个原子形成一个大的复合物体。对于实验上最相关的准一维体系，其中可积性通过有效的三体相互作用被打破，我们在使用截断维格纳方法的超越平均场模拟中发现，孤立波系综表现出相位相干性与纠缠产生之间的复杂相互作用：两个具有明确相对相位的孤立波的初始态在系综中失去该相位相干性，其单粒子双模密度矩阵表现出与退相干的双模叠加态相似的动力学。这种表观退相干是随后孤立波碰撞中形成不同原子数的纠缠叠加态的先决条件。孤立波必须首先退相干的必要性基于五次平均场方程的底层相空间进行了解释。我们在其他地方表明，不同原子数的叠加态随后会进一步演化为空间纠缠的孤立波。与典型的开放量子系统相比，在这个封闭系统中，系综相位相干性的丧失以及随后系统内部纠缠的产生以一种不寻常的顺序出现。
英文摘要：
It is an open fundamental question how the classical appearance of our environment arises from the underlying quantum many-body theory. We propose that phenomena involved in the quantum-to-classical transition can be probed in collisions of bright solitary waves in Bose- Einstein condensates, where thousands of atoms form a large compound object at ultra cold temperatures. For the experimentally most relevant quasi-1D regime, where integrability is broken through effective three-body interactions, we find that ensembles of solitary waves exhibit complex interplay between phase coherence and entanglement generation in beyond mean-field simulations using the truncated Wigner method: An initial state of two solitons with a well defined relative phase looses that phase coherence in the ensemble, with its single particle two-mode density matrix exhibiting similar dynamics as a decohering two mode superposition. This apparent decoherence is a prerequisite for the formation of entangled superpositions of different atom numbers in a subsequent soliton collision. The necessity for the solitons to first decohere is explained based on the underlying phase-space of the quintic mean field equation. We show elsewhere that superpositions of different atom numbers later further evolve into spatially entangled solitons. Loss of ensemble phase coherence followed by system internal entanglement generation appear in an unusual order in this closed system, compared to a typical open quantum system.
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