四能级倒Y型原子-环形腔耦合系统中非线性效应及窄带明亮纠缠光束产生的研究

By the interaction between the laser fields and the nonlinear medium, a nondegenerate four-wave mixing (FWM) signal is generated in the ladder-type atomic system based on electromagnetically induced transparency (EIT). Make the FWM signal resonant with the ring cavity, and then the transmission spectrum of the FWM signal is obtained. The strong-coupling regime of the atom-cavity system can be reached by controlling the temperate of the atomic system, and then the transmission spectrum of the FWM signal is studied in this regime. The influence of the atom-cavity interaction on the transmission spectrum of the FWM signal can be get through it. Another high-intensity laser field, which is called as the dressing field, interacts with the atomic system to introduce a dressing interaction to the FWM signal. So it can be theoretically and experimentally studied in the inverted-Y atomic system how the atom-cavity interaction and dressing interaction of the strong laser field impact the transmission spectrum of the FWM signal. The bight narrow-band entangled beams are experimentally generated through the FWM process in the optical cavity above the threshold. Finally, not only the generation of the many pairs of entangled beams but also their quantum correlation characters are studied in the inverted-Y system. The entangled beams which are created by use of nondegenerate four-wave mixing process in an atomic system have narrower linewidths, longer coherence times, and higher conversion efficiency, so they are useful to the long-distant quantum communication, quantum memory, etc.

通过光场与非线性原子介质的相互作用，在梯型原子能级系统中利用EIT技术产生非简并四波混频光场，使四波混频光场在环形谐振腔中谐振后输出，通过控制原子系统的温度，使原子系统和腔之间实现强耦合，研究原子系统和腔之间的强耦合对四波混频透射谱的作用；然后引入参量可控的强光场和原子系统耦合形成倒Y型能级，在此原子能级系统中，同时研究强耦合作用和强光场的光场缀饰作用对四波混频透射场的作用，实现可控性更高的非线性四波混频过程；其次利用工作于阈值以上的环形谐振腔中的四波混频过程在实验上得到明亮的具有量子关联特性的纠缠光束；最后，研究倒Y型四能级原子和腔耦合系统中存在的多对纠缠光束及这些纠缠光束的量子关联特性，为下一步实现多色纠缠做准备。利用EIT和非简并四波混频过程在原子系统中产生的纠缠光束，具有线宽窄，相干时间长和产生效率高等优点，因此本项目的研究将在远距离量子通讯，量子存储等方面产生十分重要的应用价值。

本项目针对非线性多波混频过程量子调控的国际学术前沿，围绕着光与原子相互作用过程中提高非线性效率和产生量子关联的科学问题，采用理论和实验相结合的研究方法，建立了一套腔-原子耦合系统；研究了腔-原子耦合系统中，耦合作用对多波混频过程的影响，建立了耦合强度、腔失谐、以及光场失谐和强度等参数对多波混频过程影响的关系，分析了影响腔内多波混频过程的多个因素；提出了用多波混频过程产生窄带､长相干时间､纠缠可控的非经典光源的实验方案；并利用多波混频过程开展二阶泰伯非局域成像的研究；此外，对位相以及双光子效应调控多波混频和共振荧光信号、以及在固体掺杂YSO材料中产生量子关联等方面进行了初步研究。项目的研究结果已在相关领域的国外重要期刊上发表了9篇论文，通过项目还培养了多位优秀的研究生。该项目的研究为提高非线性过程的效率提供了一种手段，为进一步利用非线性混频过程产生明亮纠缠光束提供了一种实验方案，并且在多通道窄带量子信息存储方面有一定的应用前景。关于泰伯非局域成像的研究在长距离量子图像传输中具有潜在应用价值。