基于光学超晶格中单通级联的非线性过程制备多色连续变量纠缠光场的研究

The difference between optical superlattice and bulk optical crystal is that the nonlinear coefficient can be controlled artificially in optical superlattice. Using the quasi-phase-matching technique, phase mismatches in more than one nonlinear process can be compensated in an optical superlattice. Thereby the cascaded nonlinear process can be realized and the multicolor beams with different frequencies can be produced. Because the maximum nonlinear coefficient of the crystal can be used in nonlinear process by using quasi-phase-matching technique, strong light fields can be obtained with the high nonlinear conversion efficiency. If the quantum correlation is present in the fields, by the simple device and does need the resonant cavity, one can obtain the multicolor (multipartite with different frequencies) continuous-variable entangled optical fields. Quantum entanglement is the key resources in the applications of quantum information.　With the progress of the study on quantum information, it is more and more necessary to produce multicolor continuous-variable entangled optical fields with different frequencies in order to achieve various work of quantum information. The present project brings forward several schemes of the generation of multicolor entangled optical fields through the study on quantum correlation properties among the fields produced by single-pass cascaded nonlinear process in an optical superlattice, and theoretically demonstrates its feasibility. In addition, through the study of the relationship between optical superlattice structure parameters and quantum correlation properties of the fields, this project reveals the physical mechanism about the generation of multicolor entangled optical fields.

与传统的体块光学晶体不同，光学超晶格中非线性系数可以人为调控。利用准相位匹配技术，在一块光学超晶格中可以补偿多个非线性过程中的相位失配，从而实现级联的非线性过程，产生多个不同频率光束的输出。这种利用准相位匹配技术实现的非线性过程，可以利用晶体最大的非线性系数，从而得到更高非线性转换效率，实现较强的光场输出。如果这些光场之间存在量子相关特性，则通过这种简单的装置，不需要谐振腔就可以方便地得到多色(多组份、不同频率的)连续变量纠缠光场。量子纠缠态是开展各种量子信息工作的核心资源。随着量子信息工作的不断发展，越来越迫切的需要多组份、不同频率的纠缠光源来完成各种量子信息工作。本项目通过研究光学超晶格中单通级联的非线性过程所产生多色光场之间的量子相关特性，提出若干种多色纠缠光场的制备方案，并从理论上证明其可行性。通过研究光学超晶格结构参数与光场量子相关特性之间的关系，揭示多色纠缠光场产生的物理机制。

量子信息是一门新兴的交叉学科，量子纠缠源是开展各种量子信息工作的核心资源，如何方便的制备出高纠缠度和高亮度的纠缠源，是量子信息学科重要的研究热点方向之一。利用准相位匹配技术，可以通过设计让一块光学超晶格晶体中的多个倒格矢，分别补偿多个非线性过程中的相位失配，从而可以实现多个级联的非线性过程，得到多个频率的输出光场。本项目提出了利用几个单通非线性级联过程制备连续变量纠缠光场的实验方案，采用量子随机的计算方法，并利用多组份连续变量纠缠的判据，从理论上证明了这些输出光场之间的量子纠缠特性，并讨论了光场之间的纠缠特性与泵浦光及非线性参数之间的变化关系。为实验上制备多组分不同频率明亮的高纠缠度纠缠光场提供可行的实验方案和可参考的理论数据，从而可以促进量子信息学科的应用和发展。