囚禁离子体系的快速基态冷却及非经典态制备的研究

This proposal will devote to the investigations on new schemes for fast cooling the single or multi trapped ions down to their motional ground states with high efficiency. Meanwhile, the application of these new schemes to the ground-state cooling of the nanomechanical resonators as well as to the quantum information processing based ion trapped ions will be discussed. Firstly, the research about sideband cooling of a single multi-level trapped ion will be carried out.New schemes for fast sideband cooling of the ion to its motional ground state and simitaneously to the coherent superpositions of its internal states will be put forward. For multi-atoms or multi-ions trapped in optical cavity, we will study how to cool them to their motional ground state and simultaneously prepare them in the entangled states of the internal states. A new cooling mechanism using multi-atoms entanglement to improve the cooling rate will be revealed. This may be important and useful in the realization of quantum information processing. Additionally, for the cases of the strong coupling between the ions and their oscillation phonons, or the strong coupling between the solid qubits and the nanomechanical resonantors, the physical processes described by the counter rotating-wave terms in Hamiltonian on the cooling temperature limits for the sideband-cooling will be clarified. Furthermore, novel physical processes will be designed to realize the efficient and fast cooling in the strong coupling regime. Our final goal is to make extention of the present cooling methods to a more precise and self-consistent sideband cooling theory, which can give a precise and appropriate explanation to related experimental results. How to deterministically prepare the trapped ions to their motional quantum nonclassical states will be discussed in detail.

本申请项目拟研究将单个和多个囚禁离子高效、快速冷却至其振动量子基态的新方案，并探讨这些方案在纳米机械振子的基态冷却和基于囚禁离子的量子信息技术的应用。深入研究单个多能级囚禁离子的边带冷却性质，提出高效、快速冷却囚禁离子至其振动量子基态并且同时制备于其内态相干叠加态上的新方案。探讨囚禁于光腔中多个原子（离子）的腔边带冷却性质，提出将多个原子制备于内态纠缠态，同时将它们的振动高效、快速地冷却至基态的方案，揭示利用多个囚禁原子内态量子纠缠提高冷却速率的新机制，研究这些体系用于实现量子信息处理的可能性。研究离子与其振动声子强耦合和固态量子比特与纳米机械振子强耦合时由反旋波项描述的过程对边带冷却极限温度的影响，设计新的物理过程来实现强耦合条件下高效、快速的激光边带冷却。我们还将发展精确自洽的边带冷却囚禁离子的理论，精确解释相关实验结果，设计出将离子确定性地制备于其振动量子非经典态的方案。

本项目已经按计划完成了相关的研究工作，同时将我们的研究工作拓展到量子点体系和光力机械振子系统的量子光学性质等方面。在本项目的资助下，我们发表SCI论文29篇，其中在Phys. Rev. A发表论文15篇， 在Opt. Express上发表论文6篇。课题组先后有18名研究生参加了本项研究工作，其中7人获博士学位，11人获硕士学位。取得的主要成果包括：（1）提出了利用腔诱导的双重电磁诱导透明（EIT）现象将腔中囚禁离子冷却至基态的新机制，与腔诱导的单EIT冷却机制相比，加热速率得到明显抑制，冷却速率也明显提高；提出了一个利用驻波激光场将腔中囚禁离子冷却至基态冷却方案，利用腔场光子与两个激光光子形成的三光子共振以及量子干涉效应消除蓝边带跃迁，能够实现光腔中囚禁离子的基态冷却。我们还给出了声子数高阶修正的表达式，揭示出新的量子冷却极限。提出了利用光子晶体的带隙效应来实现将强激光驱动的原子高效、快速冷却至振动基态的新方案；提出了利用量子相消干涉效应在量子点—腔场—机械振子混合体系中和双模耦合光腔—机械振子体系中将机械振子快速冷却至量子基态的新方案。（2）结合当前量子热库操控理论及实验现状，我们提出了利用光腔耗散获得两个力学振子间振动纠缠纯态的新机制；我们研究了与机械振子耦合的双模光腔系统的EPR Steering性质，发现在两腔模具有不同的弛豫速率或机械振子的阻尼较大时，输出的双模光场可以实现单向EPR Steering。在腔光力系统处于单光子强耦合区，建议了将机械振子制备于非高斯非经典态，例如压缩非高斯态、非线性相干态以及单声子态等。（3）揭示了在原子—腔场强耦合区间内非旋波项对双光子近共振激发的非相干谱和双光子阻塞效应的影响。（4）研究了量子点中电子与声子的相互作用对单量子点激光性质的影响，揭示了光子带隙和电子与声子的相互作用会量子点激光阈值的影响，提出了将腔场制备于压缩态的新方案，揭示了利用电--声耦合将级联三能级量子点制备于关联双光子态的新机制。