可恢复相干性中心自旋模型结构设计及精确动力学  

Structural Design and Exact Dynamics of a Central Spin Model with Completely Recovered Coherence

作　　者：李佳秀 LI Jia-xiu(Center for Quantum Technology Research,School of Physics,Beijing Institute of Technology,Beijing 100081,China;Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements(MOE),School of Physics,Beijing Institute of Technology,Beijing 100081,China)

机构地区：[1]北京理工大学物理学院量子技术研究中心,北京100081 [2]北京理工大学物理学院教育部高等光电量子结构与测量重点实验室,北京100081

出　　处：《量子光学学报》2022年第3期247-253,共7页Journal of Quantum Optics

摘　　要：中心自旋不可避免地与周围核自旋发生相互作用,发生退相干,这也是量子信息和量子计算领域长久以来面临的严峻挑战之一。我们提出了一种可以完美且长久保持中心自旋量子位相干性的结构,该结构由一个自旋-1/2中心自旋通过XXZ型超精细相互作用耦合上一个由非均匀耦合相互作用的自旋链构成,其在中心自旋为叠加态、浴自旋为反铁磁态为初态及浴内为较强耦合的情况下,中心自旋可近似维持原有相干性,进一步去除xy方向超精细耦合,可完美保持相干性。中心自旋作量子位,将此结构应用于量子计算,或可实现无损耗量子计算。我们用浴自旋模拟环境,应用基于XX链中自旋算符矩阵元解析表示的运动方程方法,系统地研究了环境对于中心自旋退相干动力学的影响,着重研究了浴自旋间非均匀耦合影响下的中心自旋相干因子的动力学特性。在从最小到最大调控浴自旋间非均匀耦合过程中,中心自旋相干动力学大致呈现出了六个阶段,展现了丰富的量子动力学特性,并为日后研究中心自旋动力学提供了两个重要参考标志:相干因子的长时平均值的极值可以作为区分不同相的标志;相干因子长时演化的平衡可以作为竞争平衡中耦合关系对等或之间的倍数关系的标志。The central spin inevitably interacts with the surrounding nuclear spin,resulting in decoherence,which has long been one of the severe challenges in quantum information and quantum computing.In this work,we have made some progress in this area.We propose a structure that preserves the coherence of the central spin perfectly for a long time,which consists of a spin-1/2 central spin coupled by XXZ hyperfine interaction to a spin chain interacting nonuniformly.When the central spin is in a superposition state,the bath spin is in an antiferromagnetic state as the initial state,and the coupling in the bath is strong,the central spin can approximately maintain the original coherence,and the hyperfine coupling in the xy direction is further removed,which can perfectly maintain the coherence.Using the central spin as a qubit,this structure can be applied to quantum computing,and it may realize lossless quantum computing.We use the bath spin to simulate the environment,apply the equation of motion method based on the analytical representation of the spin operator matrix element in the XX chain,and systematically study the effect of the environment on the decoherence dynamics of the central spin,focusing on the dynamics characteristics of the central spin decoherence factors under the influence of the non-uniform coupling between bath spins.In the process of controlling the non-uniform coupling between the bath spins from the minimum to the maximum,the coherent dynamics of the central spin roughly present six stages,showing rich quantum dynamic properties,and providing future research on the central spin dynamics as two important reference marks:the extreme value of the long-time mean value of the coherence factor can be used as a sign to distinguish different phases;the equilibrium of the long-time evolution of the coherence factors can be used as a sign of the equivalence or multiple relationships between the coupling relations in the competitive equilibrium.

关 键 词：量子信息 量子计算 中心自旋模型 完全恢复相干 动力学 

分 类 号：O469[理学—凝聚态物理]