Enhancement of electromagnetically induced transparency cooling by an optical cavity

We theoretically investigate an enhanced electromagnetically induced transparency （EIT） cooling method by introduc- ing a high finesse cavity. We find that the quantum destructive interference that is induced by the EIT effect and the cavity coupling can eliminate all of the heating effects in the cooling process by choosing appropriate parameters. Compared with the EIT cooling scheme, a lower final temperature can be obtained under the same conditions in our scheme.     

一种稳定的自由空间量子密钥分配实验系统

基于量子密钥分配的基本原理,采用B92方案,以单光子作为信息载体,使用极化编码,搭建了一个简单易行的实验装置,实现了自由空间传输的量子密钥分配,平均每脉冲光子数为0．1,粗码率12．7kbits／s,误码率4％左右。     

多能级原子与多模光场的相互作用机理研究

研究了多能级原子与多模光场的相互作用.探讨了旋波近似下N能级原子与(N-1)模光场相互作用演化规律，给出了相互作用绘景中其相应的Schrdinger方程的解析通式，分析了三能级原子、四能级原子分别与双模、三模光场相互作用的演化规律.研究结果表明：当原子初始时刻处于基态时，三能级原子与四能级原子的基态概率幅具有相同的变化规律. 关键词： 多能级原子 多模光场 旋波近似     

对称噪声信道下利用多纠缠态实现量子密钥分配

研究了对称噪声信道下的量子密钥分配(Quantum Key Distribution,QKD)过程，并得到了其误码率和信道保真度的关系式。基于量子态的局域区分原理，我们提出了使用“多纠缠态”进行噪声信道下的密钥分配的新方案。应用这个新方案，我们可以获得和在理想无噪声信道下使用最大纠缠态(四个Bell态之一)进行QKD一样好的结果。     

Determining spatial structures of ion crystals by simulated annealing method

Calculating the spatial structures of ion crystals is important in ion-trapped quantum computation. Here we demonstrate that the simulated annealing method is a powerful tool to evaluate the structures of ion crystals. By calculating equilibrium positions of 10 ions under harmonic potential and those of 120 ions under anharmonic potential, both with the standard procedure and simulated annealing method, we find that the standard procedure to evaluate spatial structures is complicated and may be inefficient in some cases, and that the simulated annealing method is more favorable.