基于一个三量子比特海森堡链的热纠缠研究

Thermal Entanglement of a Three Qubits Heisenberg Chain

利用Concurrence判据研究了一个三比特海森堡链的热纠缠性质.研究发现,在有限温度下,纠缠瞬间产生的现象存在于近邻纠缠C12和次近邻纠缠C13的演化中,不同的是,C12的演化中始终存在纠缠瞬间产生的现象,而C13的演化只有当温度高于临界值Tc时,这种现象才能发生.其次,温度为定值时,C12的存在范围随磁场的增大而减小,而C13的存在范围随磁场的的增大保持不变.在温度趋于0的极限情况下,C12为零,而C13达到峰值,即次近邻比特间可获得最大纠缠.此外,磁场的增大拓宽了C12和C13存在的温度的取值范围,即通过调节磁场可在较高温度获得比特间纠缠.

Using the Concurrence criterion,the thermal entanglement of a three-qubit Heisenberg chain is investigated. It is shown that the sudden birth phenomenon（ SBP） occurred in the behavior of C12 and C13. With the finite temperature,there is one apparent difference is that the sudden birth phenomenon always exits in the behavior of C12,while this phenomenon is occurred in the behavior of C13 until at a critical temperature. Furthermore,with fixed temperature,the existence region of C12 is increased initially and then decreased with increasing T,while C13 remains constant. In limit case of T→ 0,the C12 coefficient is zero,however,the C13 coefficient is reached the peak,that is to say,the maximum can be obtained between the next nearest neighbor qubits. In addition,increasing magnetic field can broaden the existence scope of temperature of C12 and C13,that is to say,the entanglement between qubits can be obtained at higher temperature by adjusting magnetic field.