非马尔科夫耗散系统长时演化下的极限环振荡现象

Phenomena of limit cycle oscillations for non-Markovian dissipative systems undergoing long-time evolution

本文研究结构化环境中非马尔科夫耗散系统在长时演化下可能出现的极限环振荡现象.对于欧姆型谱密度环境中的二能级系统,由于体系只允许一个束缚态模,给定初态系统在Bloch空间的长时演化将收敛于一个极限环.研究揭示了极限环半径与环心位置同环境谱密度函数间的关系.对于多带光子晶体环境中的二能级系统,由于其可以存在多个束缚态,研究展现了系统在长时演化下可能出现的收敛于环面或周期或准周期的振荡行为.有关环面的特征量与环境谱密度间的量化关系同样得以刻画.论文随后讨论了两比特系统关联量在局域非马尔科夫耗散环境中长时演化可能出现的特征行为.

Understanding the non-Markovian dynamics of dissipative processes induced by memory effects of the environment is a fundamental subject of open quantum systems. Because of the complexity of open quantum systems, e.g., the multiple energy scales involving that of the system, the environment, and their mutual coupling, it is generally a challenging task to characterize the relationship among the parameters of the system dynamics and the reservoir spectra. For the two-level spontaneous emission model within structured environments, it was shown in a recent literature（Opt. Lett. 38, 3650）that a functional relation could be established between the asymptotically non-decaying population and the spectral density of the reservoir as the system undergoes a long-time evolution. It hence renders a distinct perspective to look into the character of long-lived quantum coherence in the corresponding non-Markovian process. This article is devoted to further investigate the phenomena of limit cycle oscillations possibly occurring in such non-Markovian dissipative systems in a long-time evolution. For a two-level system subjected to an environment with Ohmic class spectra, due to the presence of a unique bound-state mode of the system, the evolution trajectory of the given initial states will converge to a limit cycle in the Bloch space. The dependence of the radius and the location of the limit cycle on the spectral density function of the reservoir are manifested by virtue of the described functional relation. For the model subjected to a photonic crystal environment with multiple bands, our studies reveal that, owing to the presence of two or more bound states, the evolution trajectory of the system will converge to a toric curve of a paraboloid in the Bloch space and the phenomena of periodic or quasi-periodic oscillations could exhibit. While the equation of the parabolic curve is fully determined by the initial values of the state vector in the Bloch space, our results reveal that the scope of the evolution trajectory inside the toric curve is related to the spectral density of the reservoir and their quantified relation is distinctly characterized. Finally, the asymptotic dynamics of the correlations of a two-qubit system is discussed when it is subjected locally to the non-Markovian dissipative process.