提出了一种可以精确测量有耦合的双量子比特系统的耦合项J的大小的方法.通过绝热近似计算得到了系统的哈密顿量的四个能级及其相对应的绝热本征态.利用求解得到的本征态计算分析了两低能级本征态的极化矢量,得到在对称系统中,耦合项J的大小等于使两低能级态的极化矢量长度发生突变时的外加磁场的z分量的值.此外,还利用两个不同的纠缠定义计算分析了系统的纠缠程度.在对称系统中,各个本征态的纠缠度和冯·诺伊曼熵基本相一致.
A method of measuring the exchange constant J of two-qubit system is proposed. The energy levels and eigenvectors are calculated by adiabatic approximation. The length of polarization of this system is obtained, and the value of exchange constant of symmetric system is found to equal to the value of z component of external magnetic field at the level crossing. In addition, the concurrence of each eigenvector accords with the measurement of Yon Neumann entropy for symmetry system.
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