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arXiv 1303.5564quant-phcond-mat.quant-gas
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双自旋动力学中的量子失步

Quantum loss of synchronization in the dynamics of two spins

Y. Liu, F. Piechon, J. N. Fuchs

摘要:

受最近在原子钟中观察到的自旋自重定相的启发,我们引入一个简单的动力学模型来研究退相和同步之间的竞争。两个自旋$S$被认为是最初平行的,并且在垂直于倾向于使它们退相的非均匀磁场$Δ$的平面中。此外,自旋通过交换相互作用$J$耦合,交换相互作用试图保持自旋锁定。经典动力学的解析解表明,有足够大的交换相互作用$J>Δ$相比,非均匀性的同步制度的相变。量子动力学在四个极限中解析求解-大/小$J/Δ$和大/小$S$ -以及介于两者之间的数值。与经典情况形成鲜明对比的是,量子解具有非常丰富的$S$依赖的多尺度动力学。对于任何有限的$S$,没有同步,但在两个制度之间的$J=Δ$周围的交叉。只有当$S\to \infty$以非平凡的方式接近经典解时,同步过渡才能恢复。因此,量子效应抑制了同步跃迁。

英文摘要:

Motivated by the spin self-rephasing recently observed in an atomic clock, we introduce a simple dynamical model to study the competition between dephasing and synchronization. Two spins $S$ are taken to be initially parallel and in the plane perpendicular to an inhomogeneous magnetic field $Δ$ that tends to dephase them. In addition, the spins are coupled by exchange interaction $J$ that tries to keep them locked. The analytical solution of the classical dynamics shows that, there is a phase transition to a synchronized regime for sufficiently large exchange interaction $J>Δ$ compared to the inhomogeneity. The quantum dynamics is solved analytically in four limits -- large/small $J/Δ$ and large/small $S$ -- and numerically in between. In sharp contrast to the classical case, the quantum solution features very rich $S$-dependent multiscale dynamics. For any finite $S$, there is no synchronization but a crossover around $J=Δ$ between two regimes. The synchronization transition is only recovered when $S\to \infty$, approaching the classical solution in a non-trivial way. Quantum effects therefore suppress the synchronization transition.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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