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arXiv quant-ph/0511067quant-ph
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自旋的洛伦兹变换映射

Maps for Lorentz transformations of spin

Thomas F. Jordan, Anil Shaji, E. C. G. Sudarshan

摘要:

对于具有正质量和自旋1/2的粒子,自旋密度矩阵的洛伦兹变换由开放量子动力学中使用的那种映射来描述。它们显示了自旋的洛伦兹变换如何依赖于动量。由于自旋和动量通常是纠缠的,因此映射通常不是完全正的,并且作用在有限的域中。考虑了具有两个动量值的态,因此映射是针对自旋量子比特与由两个动量值构成的量子比特纠缠的,并且可以应用来自两个耦合量子比特的开放量子动力学的结果。逆映射被用来表明,每一个洛伦兹变换完全消除了自旋极化,因此完全消除了信息,从一些自旋密度矩阵。对于特定情况,计算被去除的自旋极化的大小。

英文摘要:

Lorentz transformations of spin density matrices for a particle with positive mass and spin 1/2 are described by maps of the kind used in open quantum dynamics. They show how the Lorentz transformations of the spin depend on the momentum. Since the spin and momentum generally are entangled, the maps generally are not completely positive and act in limited domains. States with two momentum values are considered, so the maps are for the spin qubit entangled with the qubit made from the two momentum values, and results from the open quantum dynamics of two coupled qubits can be applied. Inverse maps are used to show that every Lorentz transformation completely removes the spin polarization, and so completely removes the information, from a number of spin density matrices. The size of the spin polarization that is removed is calculated for particular cases.

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