电子自旋辅助实现光子偏振态的量子纠缠浓缩  

Quantum entanglement concentration for photonic polarization state assisted by electron spin

作　　者：赵瑞通 梁瑞生[1] 王发强[1] 

机构地区：[1]华南师范大学信息光电子科技学院,广东省微纳光子功能材料与器件重点实验室,广州510006

出　　处：《物理学报》2017年第24期1-7,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61275059,61307062)资助的课题~~

摘　　要：量子纠缠浓缩可以将非最大的纠缠态转变为最大纠缠态,提高量子通信的安全性.本文基于圆偏振光和量子点-腔系统的相互作用,用一个单光子作为连接远距离纠缠光子对的桥梁,在理想条件下实现了光子偏振纠缠态的浓缩.计算结果显示,这个纠缠浓缩方案在考虑耦合强度和腔泄漏的情况下也可以保持较高的保真度,而且不需要知道部分纠缠态的初始信息,也不必重复执行纠缠浓缩过程.这不仅提高了量子纠缠浓缩的安全性,也有助于通过消耗最少的量子资源来实现高效的量子信息处理.In order to assure the security of the long-distance quantum communication, the maximum entangled state is necessary. However, the decoherence of the entanglement is inevitable because of the channel noise and the interference of the environment. Quantum entanglement concentration can be used to convert a non-maximum entangled state into a maximum one. In previous entanglement concentration proposals, we need the initial coefficients of non-maximum entangled state or repeat the entanglement concentration process to improve the possibility of success, which reduces the efficiency of the entanglement concentration. A more efficient entanglement concentration for phontonic polarization state is proposed in this paper, which is based on the interaction between circularly polarized light and quantum dot-cavity system. An auxiliary photon is introduced to connect two distant participants. To overcome the channel noise, the auxiliary photon transmits though two channels between the two participants. The photons interact with coupled quantum dot-cavity before and after the auxiliary photon transmission. Then the states of spins and auxiliary photon are measured, and the maximum phontonic polarization entangled state is obtained by single-photon operations according to the measurement results. The success possibility of the proposed scheme is 1 in ideal conditions, that is,the concentration can be realized deterministically. However, the cavity leakage is unavoidable, so the fidelity of the entanglement concentration is calculated by taking one of the measurement results for example. The results show that the influences of the initial coefficients of non-maximum entangled state on the fidelity can be ignored in most cases,which saves a mass of photons used to measure the initial coefficients of the non-maximum entangled state. The fidelities with varying coupling strengths and cavity leakages are also shown in the paper. In the case of weak coupling, the fidelity is low and varies sharply with cavity leakage. Fortunately,

关 键 词：量子纠缠浓缩 量子点 光学微腔 

分 类 号：O431.2[机械工程—光学工程]