Generation of Maximally Entangled States of Two Nonidentical Atoms in Cavity QED

We have discussed the system which consists of two nonidentical two-level atoms trapped simultaneously in a large-detuned single-mode cavity field in this paper. The results show that it is possible to generate maximally entangled states for two nonidentical two-level atoms only if the cavity frequency and difference of two nonidentical atoms transition frequency are selected and the cavity-atom interacation time is controlled.     

利用大失谐腔场中的两个原子实现量子相位门

本文讨论同时囚禁于单模、大失谐腔场中两个不同原子构成的系统,结论指出:只要仔细选择两不同原子的跃迁频率差、原子与腔场相互作用时间,可实现一个快速的量子相位门。这一方案不需要辅助的原子能级。     

Evolution of Two Non-identical Two-Level Atoms in Two-Mode Cavity Fields

In this paper, we investigate the evolution of two non-identical two-level atoms in two-mode cavity fields. We demonstrate the death and rebirth effect of entanglement for two non-identical two-level atoms under some initial conditions. It is also exemplified that entangled states of two nonidentical two-level atoms can be generated by entangled two-mode cavity fields. This research can be considered as a first step to further investigate the problem of manipulating two nonidentical two-level atoms in two-mode cavity fields.     

Enhancing entanglement generation of two atoms in a cavity with white noise using classical driving fields

We investigate the entanglement dynamics of a quantum system consisting of two two-level atoms in a cavity with classical driving fields in the presence of white noise.The cavity is initially prepared in the vacuum state.Generally,the entanglement of two atoms decreases with the intensity of the thermal fields and the coupling strength of the two-level atoms to the thermal fields.However,we find that the entanglement of the quantum system can be enhanced by adjusting the frequency and the strength of the classical driving fields in the presence of white noise.     

Remote atomic information concentration without Bell-state measurement

This paper proposes a scheme for information concentration of two remote two-level atoms in cavity QED. This scheme does not involve the Bell-state measurement. During the interaction between atom and cavity, the cavity frequency is large-detuned from the atomic transition frequency, thus the scheme is insensitive to both the cavity decay and the thermal field. This idea can directly be generalized in the case of multi-atom information concentration.     

Chaos Generation in Opto-Mechanical Coupling System Assisted by Two-Level Atoms

Chaos is important in nonlinear science and promotes the development of fundamental studies, such as neural networks, extreme event statistics, and electron transport. In this paper, a theoretical scheme for generating dynamical chaos in a Fabry–Perot cavity with two-level atoms is investigated. Through the injection of atoms, controllable chaos of the cavity and mechanical oscillator is achieved simultaneously by the external laser field. The trajectory and the maximal Lyapunov exponent that characterize the properties of the chaos could be optimized by adjusting the coupling constant, driving field, injection of atoms, the frequency of the cavity, and the frequency of the mechanical oscillator. This study provides a new idea to manipulate the cavity and mechanical chaos assisted by two level atoms. It is hoped that the results presented can benefit controllable chaos generation and its applications.     

Spontaneous emission from a system of nonidentical two-level atoms

The paper describes the main features of radiation from a system of nonidentical two-level atoms initially prepared in a specific state (just one of the atoms is excited). It is shown that in some cases the lifetime of the whole system may be shorter than the lifetime of an isolated atom.     

Three-body entanglement induced by spontaneous emission in a three two-level atoms system

We study three-body entanglement induced by spontaneous emission in a three two-level atoms system by using the entanglement tensor approach. The results show that the amount of entanglement is strongly dependent on the initial state of the system and the species of atoms. The three-body entanglement is the result of the coherent superposition of the two-body entanglements. The larger the two-body entanglement is, the stronger the three-body entanglement is. On the other hand, if there exists a great difference in three two-body entanglement measures, the three-body entanglement is very weak. We also find that the maximum of the two-body entanglement obtained with nonidentical atoms is greater than that obtained with identical atoms via adjusting the difference in atomic frequency.     

Controlling dipole squeezing of two atoms inside a cavity via manipulating an atom outside the cavity

Considering that three two-level atoms are initially in the GHZ single state and two of the atoms are simultaneously put into a cavity initially in the coherent state, we investigate the dipole squeezing properties of the two atoms inside the cavity under the condition of resonant interaction. It is shown that dipole squeezing properties of the two atoms inside the cavity are strongly affected by rotation manipulating of the atom outside the cavity.     

Generation of Maximally Entangled States for Many Two-Level Atoms in a Thermal Cavity

We propose a scheme for generating maximally entangled states for two or more two-level atoms in a thermal cavity. The cavity frequency is large-detuned from the atomic transition frequency, so the Hamiltonian can be expressed as an effective form. The photon-number-dependent parts in the effective Hamiltonian are cancelled with the assistance of a strong classical field, thus the scheme is insensitive to both the cavity decay and the thermal field. The scheme can be used to generate multi-atom Bell-state and Greenberger-Horne-Zeiliner （GHZ） state.     

利用双光子过程实现量子信息转移

提出了一个利用耦合双原子同时与大失谐的双光子Jaynes-Cummings模相互作用实现量子信息转移的方案.通过控制原子与腔场的相互作用时间及量子位的旋转操作角,可以实现原子与原子之间及原子与腔场之间的量子信息转移,而包含在欲转移量子态上的信息可被完全擦除. 关键词： 二能级原子 双光子Janeys-Cummings 模型 量子信息转移 偶极-偶极相互作用     

Entanglement of Two Atoms in Insulator and Superfluid States

We study two coupled cavities, each of which contains two two-level atoms. We identify the regions of Mott-insulator and superfluid states. Ground-state entanglement of two atoms in one cavity has been investigated. The result show that quantum entanglement of two atoms within one cavity can also characterize quantum phase transition.     

Remote Three-Atom Information Concentration without Bell-State Measurement

We propose a scheme for information concentration of three remote two-level atoms in cavity QED. Our scheme does not involve the Bell-state measurement. During the interaction between atom and cavity, the cavity frequency is largely detuned from the atomic transition frequency, thus the scheme is insensitive to both the cavity decay and the thermal field. The idea can also be used to realize the remote information concentration of trapped ions.     

光腔中两原子共振荧光的相干性质

研究了置于光腔中的两个二能级原子，在强相干场驱动下的共振荧光光场的辐射场相干性质，发现在坏腔条件下，可以通过调节光腔与相干场的频率来提高一阶可见度和减小二阶关联函数.这是因为改变光腔与相干场的频率会引起原子修饰态布居数的改变，导致一阶可见度和二阶关联函数发生显著变化. 关键词： 光腔 两个二能级原子 一阶可见度 二阶关联函数     

The emission properties of an atom inside a cavity when manipulating the atoms outside the cavity

Considering three two-level atoms initially in the GHZ state, then one atom of them is put into an initially empty cavity and made resonant interaction. It is shown that the emission properties of the atom inside the cavity can be affected only when both of the atoms outside the cavity have been manipulated. This conclusion can also be generalized to n two-level atoms.     

Controlling quantum discord dynamics in cavity QED systems by applying a classical driving field with phase decoherence

We investigate a two-level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity. We also find that the stationary quantum discord can be increased by applying a classical driving field. Furthermore, we explore the quantum discord dynamics of two identical non-interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence. Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms.     

两个双能级原子与双模腔场的拉曼相互作用

研究了两个双能级原子与双模辐射腔场的拉曼相互作用，计算了两个原子与腔场具有相同耦合常数但同时考虑原子间偶极一偶极相互作用情形下的辐射谱．讨论了双模腔场处于不同数态时辐射谱的新特点．     

Controlling quantum discord dynamics in cavity QED systems by applying a classical driving field with phase decoherence

We investigate a two-level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity.We also find that the stationary quantum discord can be increased by applying a classical driving field.Furthermore,we explore the quantum discord dynamics of two identical non-interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence.Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms.     

驱动两能级原子和真空场相互作用系统中纠缠突然死亡的操控

利用并发度和线性熵作为纠缠度量研究了两个驱动两能级原子和真空场相互作用系统中的纠缠动力学特性,分析了经典驱动场频率、原子和经典场的耦合系数以及参数α对并发度和线性熵的影响。结果发现通过调控经典驱动场能够提高两原子之间和两原子与场之间的纠缠,实现两原子之间纠缠突然死亡现象的操控,理论上提供了一种调控纠缠的方式。     

三纠缠原子与双模腔场相互作用系统的纠缠演化特性

研究了初始处于GHZ态的三个两能级原子与双模腔场相互作用系统的纠缠动力学特性,得到了并发度和线性熵的解析表达式.讨论了腔场初始纠缠度对腔内两原子之间纠缠的影响,对其余子系统求迹后结果表明腔内两原子之间的纠缠出现突然产生现象,腔内两原子之间产生纠缠的阈值时间和最大值依赖于双模腔场初始纠缠度;并且发现腔内两原子子系统和腔外原子与场子系统之间在整个的时间演化过程中一直保持着纠缠状态.