Department of Physics, Bose Institute, Kolkata, India.
J Phys Condens Matter. 2010 Jan 13;22(1):016004. doi: 10.1088/0953-8984/22/1/016004. Epub 2009 Dec 2.
We study the entanglement properties of a molecular three-qubit system described by the Heisenberg spin Hamiltonian with anisotropic exchange interactions and including an external magnetic field. The system exhibits first-order quantum phase transitions by tuning two parameters, x and y, of the Hamiltonian to specific values. The three-qubit chain is open-ended so that there are two types of pairwise entanglement: nearest-neighbour (nn) and next-nearest-neighbour (nnn). We calculate the ground and thermal state concurrences, quantifying pairwise entanglement, as a function of the parameters x, y and the temperature T. The entanglement threshold and gap temperatures are also determined as a function of the anisotropy parameter x. The results obtained are of relevance in understanding the entanglement features of the recently engineered molecular Cr(7)Ni-Cu(2+)-Cr(7)Ni complex which serves as a three-qubit system at sufficiently low temperatures.
我们研究了由海森堡自旋哈密顿量描述的分子三体系统的纠缠特性，该哈密顿量具有各向异性交换相互作用，并包括外磁场。通过将哈密顿量的两个参数 x 和 y 调谐到特定值，系统表现出一级量子相变。三体链是开放式的，因此存在两种类型的成对纠缠：最近邻（nn）和次近邻（nnn）。我们计算了作为参数 x、y 和温度 T 的函数的基态和热态的相干性，定量了成对纠缠。还确定了作为各向异性参数 x 的函数的纠缠阈值和能隙温度。这些结果对于理解最近设计的分子 Cr(7)Ni-Cu(2+)-Cr(7)Ni 复合物的纠缠特性具有重要意义，该复合物在足够低的温度下作为三体系统。
