Sun Zhe, Liu Jing, Ma Jian, Wang Xiaoguang
1] Department of Physics, Hangzhou Normal University, Hangzhou 310036, China [2] Department of Physics, National University of Singapore, Singapore 117542 [3] Singapore University of Technology and Design, 20 Dover Drive 138682, Singapore.
Zhejiang Institute of Modern Physics, Department of Physics, Zhejiang University, Hangzhou 310027, China.
Sci Rep. 2015 Feb 13;5:8444. doi: 10.1038/srep08444.
We derive an easily computable quantum speed limit (QSL) time bound for open systems whose initial states can be chosen as either pure or mixed states. Moreover, this QSL time is applicable to either Markovian or non-Markovian dynamics. By using of a hierarchy equation method, we numerically study the QSL time bound in a qubit system interacting with a single broadened cavity mode without rotating-wave, Born and Markovian approximation. By comparing with rotating-wave approximation (RWA) results, we show that the counter-rotating terms are helpful to increase evolution speed. The problem of non-Markovianity is also considered. We find that for non-RWA cases, increasing system-bath coupling can not always enhance the non-Markovianity, which is qualitatively different from the results with RWA. When considering the relation between QSL and non-Markovianity, we find that for small broadening widths of the cavity mode, non-Markovianity can increase the evolution speed in either RWA or non-RWA cases, while, for larger broadening widths, it is not true for non-RWA cases.
我们为初始状态可选择为纯态或混合态的开放系统推导了一个易于计算的量子速度极限（QSL）时间界限。此外，这个QSL时间适用于马尔可夫或非马尔可夫动力学。通过使用层级方程方法，我们数值研究了一个与单个无旋转波、非玻恩和非马尔可夫近似的展宽腔模相互作用的量子比特系统中的QSL时间界限。通过与旋转波近似（RWA）结果进行比较，我们表明反向旋转项有助于提高演化速度。还考虑了非马尔可夫性问题。我们发现，对于非RWA情况，增加系统-环境耦合并不总是能增强非马尔可夫性，这与RWA情况下的结果在定性上不同。在考虑QSL与非马尔可夫性之间的关系时，我们发现，对于腔模展宽宽度较小的情况，非马尔可夫性在RWA或非RWA情况下都可以提高演化速度，而对于展宽宽度较大的情况，在非RWA情况下则并非如此。
