Sub- and Super-Luminal Phenomena in a Doubly Driven Four-Level System

With the occurrence of an adding driving field, the properties of the dispersion and the absorption of a four-level system are changed greatly. The system can produce the normal and anomalous dispersion regions with proper parameters. Here, the driving fields can be seemed as knobs to manipulate the groupvelocity of a weak probe field between subluminal and superluminal.     

利用二粒子部分纠缠态实现开靶目标的非局域量子可控非（CNOT）门的受控操作

提出利用二粒子部分纠缠态概率性地实现开靶目标的非局域量子可控非（CNOT）门的操控方案.首先考虑利用3个二粒子部分纠缠态实现3个靶目标共享的非局域量子CNOT门的受控操作,然后将该方案推广到N个靶目标共享的情形. 在该方案中,控制端Alice的局域正定算符值测量（POVM）起着关键作用,给出了该测量算符的数学表式.值得注意的是, 用二粒子部分纠缠态可确定性地实现非局域CNOT门. 关键词： 二粒子部分纠缠态 非局域可控非门 开靶目标 正定算符值测量