量子态在包括长程相互作用磁耦极相互作用系统中传输的研究

Quantum state transmission through spin chain beyond nearest interaction

分析了量子态在包括长程相互作用自旋系统中的传输过程,分自旋传输系统处于基态和热平衡态两种不同情形进行讨论.通过自旋系统随时间的自由演化,不需要对系统进行其它的操作,就可以实现量子态从自旋链一端向另一端的传输.再选择合适的时间进行测量,可以提取得到保真度接近1的量子态.初始时刻自旋系统处于基态时,保真度随着测量时间呈准周期变化,并在0.5~1之间震荡.当自旋传输系统处于热平衡态时,最大保真度随着温度的降低而升高.无论体系初始时刻是处于基态还是处于热平衡态,当系统处于适当的外加恒定磁场中,传输效率都会提高.

The transmission of quantum state through spin chain which is beyond the nearest interaction is studied in two cases ,the one is that spin chain is initially in ground state, and the other is in the thermal equilibrium state. Without any operation on the spin chain, quantum state can be transferred from one site to another different site naturally through the spin interaction. By choosing proper measurement time,one can get high fidelity near 1. When the spin chain is prepared in the ground state,fidelity oscillation between 0.5 and 1 is changed in quasi-period style as the measurement time is changed. In another case the spin chain is prepared in thermal equilibrium state,the maximum fidelity is increased as the temperature decline. In both cases, the transmission efficiency can be improved through appropriate external magnetic field.