Transferring of a Two-Mode Entangled State Between Two Cavities via Cavity QED

We propose a scheme for transferring of a two-mode entanglement of zero- or one-photon entangled states between two cavities via atom-cavity field resonant interaction. In our proposal, in order to transfer the entangled state, we only need two identical two-level atoms and a two-mode cavity for receiving the teleported state. This scheme does not require Bell-state measurement and performing any transformations to reconstruct the initial state. And the transfer can occur with 100% success probability in a simple manner. And a network for transferring of a two-mode entangled state between cavities is suggested. This scheme can also be extended to transfer N-mode entangled state of cavity.     

利用V-型三能级原子与双模腔场双光子大失谐相互作用制备W纠缠态

本文提出利用V-型三能级原子与双模腔场的双光子大失谐相互作用制备W纠缠态,该方案要求三个三能级原子和一个双模腔场,第一个与腔场作用的原子最初处于激发态,第二个和第三个原子均处于基态,腔场最初处于真空态,合适地选择原子与腔场之间的相互作用时间即可获得三原子W纠缠态.并且此方案可以推广至多原子W纠缠态和多腔场W纠缠态的制备;通过计算共生纠缠度研究系统中态的纠缠演化以及热纠缠现象.     

利用V-型三能级原子与双模腔场 双光子大失谐相互作用制备W纠缠态

本文提出利用 型三能级原子与双模腔场的双光子大失谐相互作用制备W纠缠态,该方案要求三个三能级原子和一个双模腔场,第一个与腔场作用的原子最初处于激发态,第二个和第三个原子均处于基态,腔场最初处于真空态,合适地选择原子与腔场之间的相互作用时间即可获得三原子W纠缠态。并且此方案可以推广至多原子W纠缠态和多腔场W纠缠态的制备;通过计算共生纠缠度研究系统中态的纠缠演化以及热纠缠现象。     

Generation of fully three-mode continuous-variable entanglement in a single-atom laser

We proposed a scheme for generating fully three-mode continuous-variable (CV) entanglement between three nondegenerate cavity modes in a single-atom laser. In our scheme, the single-atom laser consists of a four-level atom inside a triply resonant cavity, and the atomic coherence is induced by two classical laser fields driving the corresponding atomic transitions. To demonstrate the generation of entanglement, we numerically simulated the dynamics of this system, and the numerical simulation shows that the single-atom laser considered here can be seen as a three-mode CV entanglement amplifier even in the presence of cavity losses. Moreover, we also show that the generation of entanglement doesn’t depend intensively on the initial condition of cavity field, and the fully three-mode CV entanglement can be realized no matter the three entangled (nondegenerate) modes are initially in the same state or different states based on our scheme.     

基于四波混频过程的纠缠光放大

双模纠缠态是量子信息领域一种重要的量子资源,本文基于四波混频过程从理论上提出了对双模纠缠态的单个模式(单模放大方案)和对双模纠缠态的两个模式(双模放大方案)的放大.利用光学分束器模型来模拟在光学传输过程中损耗引入的真空场噪声,利用部分转置正定判据分析了两种不同的放大方案中四波混频过程的增益对初始双模纠缠态的纠缠程度的影响.结果表明,在特定的损耗情况下,两个方案中初始双模纠缠态的纠缠度都随增益的增大而减小,直至消失,且双模放大方案中初始双模纠缠态纠缠消失得比单模放大方案中更快.本文的理论结果为实验上实现基于四波混频过程的双模纠缠态的放大奠定了理论基础.     

Generation of two-mode entangled states in a four-level atomic system via the Raman process

In this paper, we have theoretically investigated the generation of two-mode entangled states from a four-level atomic system via the Raman process. We show that the degree of entanglement between the two cavity modes could be strongly adjusted by both the Rabi frequencies and the detunings of the pumping fields. Our numerical results reveal that entanglement between the steady state of the two cavity modes depends on the difference of the two detunings of the atomic levels with the classical laser fields or the difference of the two Rabi frequencies. Finally, our result also shows that when such atomic system is operated above the threshold, it is possible to obtain the macroscopic entangled states.     

Entanglement reciprocation between two charge qubits and two-cavity field

We propose a simple scheme to generate two-mode entangled coherent state in two separated cavities and realize the entanglement reciprocation between the superconducting charge qubits and continuous-variable system. By measuring the state of charge qubits, we find that the entanglement of two charge qubits, which are initially prepared in the maximally entangled state, can be transferred to the two-cavity field, and at this time the two-cavity field is in the entangled coherent state. We also find that the entanglement can be retrieved back to the two charge qubits after measuring the state of the two-cavity field.     

增光子二模纠缠相干态的纠缠特性及其通过腔量子电动力学的制备

分析了增光子二模纠缠相干态的纠缠特性,得到共生纠缠度的解析表示式.结果表明:增光子二模纠缠相干态的共生纠缠度与叠加态的相位有非常灵敏的关系.提出了一种制备增光子相干态和增光子二模纠缠相干态的方法,其制备过程为首先把增光子相干态转化为相干态与真空态一种特殊的叠加态(叠加系数与相干态振幅有关),再通过位于高Q腔内的原子与经典激光场的相互作用,从而实现增光子相干态的制备.通过一个飞行原子先后与两个光腔中光场相互作用可以实现增光子二模纠缠相干态的制备.     

增光子二模纠缠相干态的纠缠特性及其通过腔量子电动力学的制备

分析了增光子二模纠缠相干态的纠缠特性,得到共生纠缠度的解析表示式.结果表明:增光子二模纠缠相干态的共生纠缠度与叠加态的相位有非常灵敏的关系.提出了一种制备增光子相干态和增光子二模纠缠相干态的方法,其制备过程为首先把增光子相干态转化为相干态与真空态一种特殊的叠加态(叠加系数与相干态振幅有关),再通过位于高Q腔内的原子与经典激光场的相互作用,从而实现增光子相干态的制备.通过一个飞行原子先后与两个光腔中光场相互作用可以实现增光子二模纠缠相干态的制备.     

Continuous-variable Entanglement in a Correlated Spontaneous Emission Laser

We discuss the generation and evolution of entangled light in a correlated spontaneous emission laser in the linear regime. The master equation for the two-mode cavity field is derived and solved analytically in phase space. The time-dependent characteristic function in the Wigner representation for the two-mode field is obtained. It shows that the two-mode field in the cavity evolves in a two-mode Gaussian state. The entanglement degree of the two- mode field in the cavity increases initially, then decreases, and finally vanishes as the field evolves from an initial vacuum. The period of the entanglement is extended as the intensity of the driving field is increased. It is found that the entanglement still exists even when the two-mode squeezing disappears. During the entanglement period, the intensity of the field is amplified. The entanglement for the initial field being a two-mode squeezed vacuum and the entanglement of the output field are also discussed.     

Entanglement reciprocation between two charge qubits and two-cavity field

We propose a simple scheme to generate two-mode entangled coherent state in two separated cavities and realize the entanglement reciprocation between the superconducting charge qubits and continuous-variable system. By measuring the state of charge qubits, we find that the entanglement of two charge qubits, which are initially prepared in the maximally entangled state, can be transferred to the two-cavity field, and at this time the two-cavity field is in the entangled coherent state. We also find that the entanglement can be retrieved back to the two charge qubits after measuring the state of the two-cavity field.      

利用两能级原子与腔场相互作用实现纠缠压缩态的纠缠浓缩

根据大失谐条件下原子-腔场相互作用的特点,讨论了一个制备纠缠压缩态的方法,提出了一个利用两能级原子与腔场相互作用实现纠缠压缩态纠缠浓缩的方案。在这个方案中,两束具有相同振幅但有着 相位差的压缩光 和 构成的纠缠态光场被用来作为量子信道。通过利用两能级原子与腔场的相互作用以及两模正交态测量实现了这个纠缠浓缩的过程。结果表明：对于纠缠压缩态,无论其初始的纠缠是多么微弱,利用这种方法总有一定的几率可以从部分纠缠态中提取出最大纠缠态。     

利用置于光腔中的非线性耦合器制备压缩和连续变量纠缠光

利用置于光腔中的非线性耦合器制备了压缩和连续变量纠缠光.通过特征函数方法解析求解了双模腔场满足的主方程.分析发现：在一定的条件下,此系统能产生稳定的双模压缩和连续变量纠缠光,且压缩和纠缠的强度与系统的耦合参量及腔场损耗系数密切相关.     

Entanglement generation in a two-mode single-atom laser

We present a method of generating two-mode single atom laser based on the nonresonant interaction of a three-level Λ type atom in a two-mode cavity with three strong classical driving fields. An analytical solution for this effective dynamics under the presence of the cavity losses is obtained, which allow us to analyze the entanglement properties and the photon statistics of the two cavity modes exactly. It is also shown that the possible generation of the two-mode entangled coherent states in the transient regime after the atomic measurement.     

远程制备双原子纠缠态

提出一种远程制备双原子纠缠态的方案,该方案基于两个原子与单模腔场的同时非共振相互作用.由于双粒子纠缠态比三粒子纠缠态容易制备,方案用两对双原子纠缠态作为量子通道.Alice 拥有的两个相同原子同时与一单模腔场非共振相互作用.Alice已知她要制备的纠缠态,她选择适当的相互作用时间、测量她所拥有的两个原子并通过经典通道通知Bob.Bob引入一个相同的辅助原子和一个单模腔场来实现方案.方案对腔场状态和腔损耗不敏感,基于当前的腔QED 技术,方案能在实验上实现.该方案有望在量子信息过程中有重要的应用价值.     

V-型三能级原子与双模腔场模型中的纠缠交换方案

文章利用V-型三能级原子与双模腔场双光子共振相互作用,提出了一种纠缠交换的方案制备最大纠缠态,此方案不需要Bell基测量,只需对单个原子进行测量,就能实现初始没有直接相互作用的原子与腔场之间产生纠缠,合适选择原子与腔场之间的相互作用时间可获得具有最大保真度以及成功几率的最大纠缠态,另外,还讨论了该方案的实验可行性.     

Entanglement transfer from two-mode squeezed vacuum light to spatially separated mechanical oscillators via dissipative optomechanical coupling

In this paper, we propose a scheme to generate an entangled state between two spatially separated movable mirrors by injecting the two-mode squeezed optical reservoir to the dissipative optomechanics, in which the movable mirrors can modulate the linewidth of the cavity modes. When the coupling between the mirrors and the corresponding cavity modes is weak, the two driven cavity fields can respectively behave as the squeezed-vacuum reservoir for the two movable mirrors by utilizing the effect of completely destructive interference of quantum noise. Thus the mechanical modes are prepared in a two-mode squeezed vacuum state. Moreover,when the coupling between the two mirrors and the cavities modes is strong, the entanglement between the two movable mirrors decreases because photonic excitation can preclude the completely destructive interference of quantum noise, but the movable mirrors are still entangled.     

微波驱动双模四能级单原子中连续变量纠缠的制备

通过两个经典微波场驱动相应的原子精细跃迁诱导产生原子相干, 研究在双模单原子激光器中连续变量量子纠缠的制备和演化. 研究结果表明: 微波场强度可以有效地控制腔场纠缠特性; 通过调节相应的频率失谐, 能够同步增加腔场总的平均光子数、腔模间的纠缠时间和强度. 关键词： 四能级单原子 原子相干 连续变量纠缠     

纠缠微波信号的特性及表示方法

纠缠微波信号是电磁场微波频段量子特性的体现.在总结了现有纠缠微波信号产生及验证实验的基础上,针对目前没有统一的表达式来描述纠缠微波信号格式的问题,通过深入分析纠缠微波信号的特性,提出了两种纠缠微波信号的表示方法.一种是在量子框架下,利用双模压缩真空态表示,并分别在光子数表象下和Wigner分布下分析了其信号特征,刻画了正交分量之间的正反关联特性;另一种是在经典框架下,利用关联随机信号表示,刻画了测量后纠缠微波信号场幅度正交分量随时间变化的波形图.两种表示恰当合理地反映了纠缠微波信号连续变量纠缠的特性.     

Generation of an Entangled State of Two Three-Level Superconducting Quantum Interference Devices in Cavity

We propose a scheme for generating a maximally entangled state of two three-level superconducting quantum interference devices (SQUIDs) by using a quantized cavity field and classical microwave pluses in cavity. In this scheme, no quantum information will be transferred from the SQUIDs to the cavity since the cavity field is only virtually excited. Thus, the cavity decay is suppressed during the entanglement generation.