与反铁磁环境耦合的中心自旋的几何相位
Geometric phase of a central spin coupled to an antiferromagnetic environment
摘要：
利用自旋波近似，研究了在外加全局磁场作用下，中心自旋（信号量子比特）与反铁磁（AF）环境耦合的几何相位（GP）。外部磁场直接影响量子位的GP，也通过其对AF环境的影响间接影响。我们发现，当外加磁场增加到临界磁场点时，AF环境发生自旋翻转转变，即一阶相变，同时量子比特的GP突变为零.信号量子比特的GP在临界点附近对多体环境参数变化的敏感性可以作为研究多体相变的另一种有效工具或证据。研究了AF环境温度和晶体各向异性场对GP的影响。
英文摘要：
Using the spin-wave approximation, we study the geometric phase (GP) of a central spin (signal qubit) coupled to an antiferromagnetic (AF) environment under the application of an external global magnetic field. The external magnetic field affects the GP of the qubit directly and also indirectly through its effect on the AF environment. We find that when the applied magnetic field is increased to the critical magnetic field point, the AF environment undergoes a spin-flop transition, a first-order phase transition, and at the same time the GP of the qubit changes abruptly to zero. This sensitive change of the GP of a signal qubit to the parameter change of a many-body environment near its critical point may serve as another efficient tool or witness to study the many-body phase transition. The influences of the AF environment temperature and crystal anisotropy field on the GP are also investigated.
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