M光子Jaynes-Cummings模型中场的N阶压缩

推广了通常压缩和振幅平方压缩的概念,定义了N阶压缩,讨论了在M光子J-C模型中的N阶压缩。结果表明:对偶数M,周期性出现压缩;对奇     

PHOTON STATISTICS OF THE MICROMASER WITH ULTRA COLD Λ-TYPE THREE-LEVEL ATOMS

We have established the master equation for the micromaser with the ultra-cold Λ-type three-level atoms and studied the photon statistics of the micromaser field. We find that as the atoms become colder,the change of the mean photon-number and the normalized standerd deviation become more regular, and their resonance peaks become sharper. For zero-temperature cavity,there are some regins in which the photon statistics are sub-Poissonian.With the increase of the cavity temperature,both the mean photon-number and the normalized standard deviation increase. When the cavity temperature is high enough, the sub-Poissonian property may disappear.     

Phase modulation polarization encoding module applied to one-to-many QKD network based on wavelength division multiplexing

The quantum key distribution(QKD) network is a promising solution for secure communications. In this paper, we proposed a polarization-independent phase-modulated polarization encoding module, and it can be combined with a dense wavelength division multiplexer(DWDM) to achieve multi-user QKD. We experimentally test the encoding module with a repetition rate of 62.5 MHz, and its average quantum bit error rate(QBER) is as low as 0.4%. Finally, we implement a principle verification test for simulta...     

Decoherence of two-qubit system in a non-Markovian squeezed reservoir

The decoherence of two initially entangled qubits coupled with a squeezed vacuum cavity separately is investigated exactly. The results show that, first, in principle, the disentanglement time decreases with the increase of squeeze parameter r, due to the augmenting of average photon number of every mode in the squeezed vacuum cavity. Second, there appear entanglement revivals after the complete disentanglement for the case of even parity initial Bell state, while there occur the entanglement decrease and the entanglement revival before the complete disentanglement for the case of odd parity initial Bell state. The results are quite different from those for the case of qubits in a vacuum cavity.     

从离散Wigner函数的角度探讨量子相干性度量

量子相干性是量子信息处理的基本要素,在量子计算中扮演着重要的角色.为了便于讨论量子相干性在量子计算中的作用,本文从离散Wigner函数角度对量子相干性进行了探讨.首先对奇素数维量子系统的离散Wigner函数进行了分析,分离出表征相干性的部分,提出了一种可能的基于离散Wigner函数的量子相干性度量方法,并对其进行了量子相干性度量规范的分析;同时也比较了该度量与l_1范数相干性度量之间的关系.重要的是,这种度量方法能够明确给出量子相干性程度与衡量量子态量子计算加速能力的负性和之间不等式关系,由此可以解析地解释量子相干性仅是量子计算加速的必要条件.     

Stationary entanglement between two nanomechanical oscillators induced by Coulomb interaction

We propose a scheme for entangling two nanomechanical oscillators by Coulomb interaction in an optomechanical system. We find that the steady-state entanglement of two charged nanomechanical oscillators can be obtained when the coupling between them is stronger than a critical value which relies on the detuning. Remarkably, the degree of entanglement can be controlled by the Coulomb interaction and the frequencies of the two charged oscillators.     

超冷V型三能级原子注入的微波激射:原子相干性对腔场光子统计的影响

建立了超冷V型三能级原子注入的微波激射的腔场光子统计的量子理论,研究了原子相干性对光子统计性质的影响.发现腔内原子的发射概率随腔长变化的曲线中存在着共振峰和非共振平台,原子相干性对这些共振峰和非共振平台的绝对大小和相对比例具有灵活的可调性.原子发射概率的这些特点对腔场光子统计产生了直接的影响.平均光子数随腔长变化的曲线中也存在着共振峰和非共振平台;给定腔长,适当调节原子相干参量,可以使光子数分布向大、小光子数两个方向灵活地移动,平均光子数也相应地增加和减少.研究中还发现,适当选取原子相干参量,光子统计在大 关键词： 微波激射 超冷V型三能级原子 原子相干性 光子统计     

Adjustable quantum coherence effects in a hybrid optomechanical system

We propose a system for achieving some adjustable quantum coherence effects, including the normal-mode splitting(NMS), the optomechanically induced transparency(OMIT), and the optomechanically induced absorption(OMIA). In this system, two tunnel-coupled optomechanical cavities are each driven by a coupling field and coupled to an atomic ensemble.Besides, one of the cavities is also injected with a probe field. When the system works under different conditions, we can obtain the NMS, the OMIT, and the OMIA, respectively. These effects can be flexibly adjusted by the tunnel coupling between the two cavities, the power of the coupling lasers, and the coupling strength between the atomic ensembles and the cavity fields. Furthermore, we can realize the OMIT even if the oscillating mirrors have relatively larger decay rates.     

One-step implementation of an N-qubit quantum phase gate through a double Raman passage

We propose a scheme for controllably implementing an N-qubit phase gate by one step within a ground-state subspace of N three-state atoms trapped in a cavity through a double Raman passage.We can extend our scheme to the realisation of an arbitrary N-qubit phase gate by appropriately adjusting coupling strengths and detunings between atoms and external driving fields.The advantage of this one-step scheme is its robustness against decoherence.     

Kerr介质中耦合双原子的纠缠特性

研究了Kerr介质中两个耦合二能级原子的纠缠演化规律, 通过concurrence计算了系统的纠缠度, 讨论了系统初态、Kerr 介质和原子之间的偶极相互作用对腔中两个原子纠缠度的影响. 结果表明: 通过适当选取Kerr介质的耦合系数和偶极相互作用强度, 可以获得固定的两原子纠缠, 并且可以提高两原子之间的纠缠, 甚至彻底消除纠缠猝死现象. 关键词： 偶极相互作用 Kerr介质 concurrence