Finite-time Landau-Zener processes and counterdiabatic driving in open systems: Beyond Born, Markov, and rotating-wave approximations
Finite-time Landau-Zener processes and counterdiabatic driving in open systems: Beyond Born, Markov, and rotating-wave approximations
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DOI：
10.1103/physreva.93.012121
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发表时间：
2015-11
影响因子：
2.9
通讯作者：
Zhe Sun;Longwen Zhou;G. Xiao;D. Poletti;J. Gong
中科院分区：
文献类型：
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作者：
Zhe Sun;Longwen Zhou;G. Xiao;D. Poletti;J. Gong
我们研究了由两级量子系统建模的朗道-齐纳过程，其有限偏置能量随时间变化，并且在零温度下存在单个展宽腔模式。通过将层次方程方法应用于朗道-齐纳问题，我们通过计算研究了没有玻恩、马尔可夫、旋转波或其他微扰近似的绝热态的生存保真度。通过这种处理，还可以研究具有非常强的系统-浴耦合的情况。与之前对无限时间朗道-齐纳过程的研究不同，与瞬时绝热状态相比，时间演化状态的保真度显示出对系统浴耦合和偏置扫描速率的非单调依赖性。然后，我们考虑应用反绝热驱动场的效果，发现仅对于足够短的朗道-齐纳过程，这才有助于提高保真度。精确的数值结果表明，不同的反绝热驱动场对环境影响的鲁棒性可能有很大不同。最后，通过案例研究，我们讨论了引入动态解耦场的可能性，以消除环境的退相干效应，同时保留反绝热场的积极作用。我们的工作表明，具有反绝热驱动的有限时间朗道-齐纳过程为理解开放系统中的受控绝热过程提供了一个富有成效的测试平台。
We investigate Landau-Zener processes modeled by a two-level quantum system, with its finite bias energy varied in time and in the presence of a single broadened cavity mode at zero temperature. By applying the hierarchy equation method to the Landau-Zener problem, we computationally study the survival fidelity of adiabatic states without Born, Markov, rotating-wave or other perturbative approximations. With this treatment it also becomes possible to investigate cases with very strong system-bath coupling. Different from a previous study of infinite-time Landau-Zener processes, the fidelity of the time-evolving state as compared with instantaneous adiabatic states shows non-monotonic dependence on the system-bath coupling and on the sweep rate of the bias. We then consider the effect of applying a counter-diabatic driving field, which is found to be useful in improving the fidelity only for sufficiently short Landau-Zener processes. Numerically exact results show that different counter-diabatic driving fields can have much different robustness against environment effects. Lastly, using a case study we discuss the possibility of introducing a dynamical decoupling field in order to eliminate the decoherence effect of the environment and at the same time to retain the positive role of a counter-diabatic field. Our work indicates that finite-time Landau-Zener processes with counter-diabatic driving offer a fruitful test bed to understand controlled adiabatic processes in open systems.