玻色-爱因斯坦凝聚体中猫态的产生、判定及退相干问题的研究

Entanglement is considered to be one of the most fundamental features of quantum mechanics and the key resource in quantum information science. In particular, macroscopic quantum superposition states embody the famous paradox formulated by Schr?dinger that quantum mechanics admits the existence of a cat in a quantum superposition of "dead" and "alive" states. This leaves an important open question. Will nonlocal quantum phenomena still persist at a large scale? And do quantum superpositions survive in this limit? However, it is certainly not trivial to create states that are macroscopic quantum superpositions. Such experiments require the utmost delicacy and precision. Despite the difficulties, if macroscopic superpositions can be created, one has vindicated the most unlikely sounding predictions of quantum theory. Cat states have implications in ultra-sensitive measurements - and could also revolutionise our understanding of the universe. ..An excellent candidate for Cat States is a Bose-Einstein condensate in a double well which gives one hope to observe the first truly large scale Cat States of matter. The primary aim of this research project is to develop a description of macroscopic entanglement for a Bose-Einstein condensate (BEC) and use it to study the properties of a range of realistic physical systems. We aim to investigate the interpretation of the Schr?dinger cat superposition in ultracold atomic and nanomechanical systems, given known sources of environmental heating and loss. We will show how to identify and test these states and effects of decoherence and entanglement generation in the dynamics of Bose-Einstein condensates. A key challenge in modern physics is the design of robust methods for not only generating entanglement, but also developing methods to maintain Cat states for as long as they are required. The project will enhance understanding at this level. In the face of emerging technologies, there is an opportunity for testing mesoscopic/macroscopic realism versus quantum mechanics using novel developments in low-temperature physics. The proposed research program provides an essential link between theory and experiments of much future significance.

"薛定谔猫"态是由大量空间可分辨的微观粒子组成的宏观系统中呈现出的整体量子现象。本质上它是一种大尺度的量子纠缠态，而量子纠缠是量子力学最根本的特征之一，也是量子信息科学的关键资源。因此，"薛定谔猫"态不仅能帮助我们研究量子物理的基本问题，还在精密测量和量子信息处理等方面具有很高的实际应用价值。..本项目是从全量子理论出发探讨超冷原子BEC中的宏观量子叠加效应，研究可直接用于EPR佯谬和"薛定谔猫"佯谬的猫态，深入分析猫态随时间的动力学演化。项目的研究重点在于寻找猫态的纠缠特征，即如何识别和测量猫态，研究退相干的影响，找到延长猫态寿命的办法，为未来实现更大尺度的介观相干叠加乃至宏观尺度上的量子纠缠提供科学依据，进而寻找其在超精密测量和量子信息处理过程中的潜在应用前景。

"薛定谔猫"态是由大量空间可分辨的微观粒子组成的宏观系统中呈现出的整体量子现象。本质上它是一种大尺度的量子纠缠态，而量子纠缠是量子力学最根本的特征之一，也是量子信息科学的关键资源。因此，"薛定谔猫"态不仅能帮助我们研究量子物理的基本问题，还在精密测量和量子信息处理等方面具有很高的实际应用价值。在超冷原子玻色爱因斯坦凝聚系统中研究量子相干和量子纠缠，将对量子力学基本问题、量子信息的物理实现、以及超精密测量等方面产生重要的影响。..本项目研究了超冷原子玻色爱因斯坦凝聚体系中的宏观量子叠加效应，包括多原子量子纠缠、模式纠缠、自旋压缩等，探讨了纠缠和压缩在相位精密测量方面的应用（多篇PRA等）。研究了连续变量多模光场系统以及含有冷原子的腔光力复合量子系统中丰富的纠缠结构和动力学行为，探索了其在远程量子通信网络方面的可能应用，为未来实现更大尺度上的量子纠缠提供理论依据（多篇PRA，OL等）。系统研究了多体量子纠缠的分类判定问题，对量子非定域性、导引、不可分等三种纠缠类型给出了形式简单且易于实验检验的判定不等式（1篇PRL，多篇PRA等），特别对量子导引在定性检验、定量度量、性质刻画，及其在量子信息领域的应用等多方面进行了深入研究，取得了从两体到多体量子导引研究的关键突破，并与实验合作首次实现了连续变量光场的多体量子导引，形成了系统性的理论框架和研究特色（1篇Nat. Phys.，1篇PRL，多篇PRA等）。..在项目支持下共发表（含接收）期刊论文18篇，其中SCI论文16篇（第一/通讯作者15篇），包括：Nature Physics 1篇（共同通讯作者），Physical Review Letters 2篇（第一作者）, EI论文1篇，科普性介绍论文1篇。参加国际会议并作邀请报告8次。