1.College of Physical and Electronic Information, Luoyang Normal College, Luoyang 471022, China 2.School of Information Engineering, Guangdong Medical University, Dongguan 523808, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant No. 11804141), the Training Plan of Young Key Teachers in Colleges and Universities of Henan Province, China (Grant No. 2018GGJS129), the Key Science and Technology Project of University of Henan Province, China (Grant No. 16A140013), the Doctoral Program of Guangdong Natural Science Foundation, China (Grant No. 2018A030310109), and the Doctoral Project of Guangdong Medical University, China (Grant No. B2017019)
Received Date:14 July 2019
Accepted Date:17 September 2019
Available Online:27 November 2019
Published Online:05 December 2019
Abstract:The quantum system decay can be frozen and slowed down when it is repeatedly and frequently measured, which is described as the quantum Zeno effect (QZE). On the other hand, the evolution of the quantum system can be sped up if the measurement is not frequent enough, which is called quantum anti-Zeno effect (QAZE). Both the QZE and QAZE have been experimentally observed in many different physical setups, and have attracted tremendous theoretical and experimental interest due to their significant potential applications in quantum information processing.A recent research has demonstrated that the effective lifetime of the quantum system when being measured repeatedly depends on the spectral density of the environment, the system parameters, and the system-environment coupling. Then, how to prolong the survival time of the quantum system subjected to being repeatedly measured is an issue that deserves to be studied. In the present paper, considered is a classical-field-driven two-level system interacting with a bosonic reservoir at zero temperature. We investigate the dynamics of the effective decay rate versus the measurement interval, and propose a scheme to prolong the lifetime of the quantum system subjected to being measured repeatedly, with a classical field driven. The results show that when the initial state of the quantum system is excited, QZE-to-QAZE transitions occurs several times. In an identical time interval, the decay rate for the initial superposition state is far smaller than that for the initial excited state. More importantly, the effective decay rate is very small when the classical driving is strong enough, which indicates that the classical driving can improve the survival probability of the two-level system subjected to being measured frequently and repeatedly. In addition, the environmental ohmicity plays an important role in keeping the quantum state alive. The detuning between the two-level system and the classical field has an adverse effect on the decay rate. In other words, the survival probability decreases as the detuning increases. Fortunately, this negative influence from the detuning can be suppressed by increasing the strength of classical driving or choosing the appropriate ohmicity parameter of the environment. Keywords:quantum Zeno effect/ classical driving/ effective decay rate/ survival probability
4.量子Zeno效应和量子反Zeno效应根据上一节的计算结果, 分别展示共振和非共振条件下有效衰减率随测量间隔的变化(图1和图2). 此外, 也讨论了二能级系统初始处于非叠加态时的情形(图3). 图 1 有效衰减率随测量间隔的变化曲线 (a) $s = 0.5$; (b) $s = 1$; (c) $s = 2$ Figure1. The behavior of the effective decay rate as a function of the measurement interval: (a) $s = 0.5$; (b) $s = 1$; (c) $s = 2$.
图 2 有效衰减率随测量间隔的变化曲线 (a) $\varOmega = 30$, $s = 0.5$; (b) $\varOmega = 30$, $s = 2$; (c) $\varOmega = 50$, $s = 2$ Figure2. The beehavior of the effective decay rate as a function of the measurement interval: (a) $\varOmega = 30$, $s = 0.5$; (b) $\varOmega = 30$, $s = 2$; (c) $\varOmega = 50$, $s = 2$.
图 3 初态$|\psi \rangle = {\rm{|}}1\rangle $时有效衰减率随测量间隔的变化曲线 Figure3. Behavior of the effective decay rate as a function of the measurement interval for the initial state $|\psi \rangle = {\rm{|}}1\rangle $.