经典场驱动对量子系统生存概率的影响

Influence of classical field driving on survival probability in quantum Zeno and anti-Zeno effect

考虑一个受经典场驱动的二能级系统与零温玻色子库相互作用,研究经典场驱动对量子Zeno效应和量子反Zeno效应中量子系统存活概率的影响.结果表明,经典场驱动可以降低量子系统的有效衰减率,即提高量子系统的存活概率.此外,环境的欧姆性对于提高量子系统的存活概率也起着重要作用,设置适当的环境欧姆参数可降低量子系统的有效衰减率.再者,随着二能级系统与经典场之间失谐量的增加,量子系统的存活概率降低,而通过增加经典场驱动的强度或选择合适的环境欧姆参数,可以抑制失谐带来的负面影响.

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 systemenvironment 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-fielddriven 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.