Kudo K, Monteiro T S
Department of Applied Physics, Graduate School of Engineering, Osaka City University, Osaka 558-8585, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 May;77(5 Pt 2):055203. doi: 10.1103/PhysRevE.77.055203. Epub 2008 May 29.
We investigate quantum dynamics in phase-space regions containing "shearless tori." We show that the properties of these peculiar classical phase-space structures-important to the dynamics of tokamaks-may be exploited for quantum information applications. In particular we show that shearless tori permit the nondispersive transmission of localized wave packets. The quantum many-body Hamiltonian of a Heisenberg ferromagnetic spin chain, subjected to an oscillating magnetic field, can be reduced to a classical one-body "image" dynamical system which is the well-studied Harper map. The Harper map belongs to a class of Hamiltonian systems (nontwist maps) which contain shearless tori. We show that a variant with sinusoidal time driving "driven Harper model" produces shearless tori which are especially suitable for quantum state transfer. The behavior of the concurrence is investigated as an example.
我们研究了包含“无剪切环面”的相空间区域中的量子动力学。我们表明，这些特殊的经典相空间结构的性质——对托卡马克动力学很重要——可被用于量子信息应用。特别是，我们表明无剪切环面允许局域波包的非色散传输。一个受到振荡磁场作用的海森堡铁磁自旋链的量子多体哈密顿量，可以简化为一个经典的单体“图像”动力学系统，即经过充分研究的哈珀映射。哈珀映射属于一类包含无剪切环面的哈密顿系统（非扭转映射）。我们表明，具有正弦时间驱动的变体“驱动哈珀模型”会产生特别适合量子态转移的无剪切环面。作为示例，研究了并发度的行为。
