基于表面等离子体的集成量子光学器件研究

With the increase in complexity of realizable quantum architectures,the need for stability and high quality nonclassical interference within large optical circuits has become a matter of concern in modern quantum optics. Using integrated waveguide structures, integrated quantum photonic chips show us a high performance platform from which to further develop quantum technologies and experimental quantum physics using single photons. Quantum state preparation, manipulation, and measurement as well as the first on-chip quantum metrology experiments have been demonstated based on silica-on-silicon waveguide. Most recently, several two-photon quantum controlled logic gates are also realized in experiments with high quality. While the size of the silica-on-silicon waveguide cannot be samller than wavelength due to the diffraction litmit, and the manipulation of polarization which is one of the most important properties for light is still a challenge in integrated optical systems, since the propagation of light in dielectric waveguides is insensitive to the polarization. Surface plasmon, collective oscillating electrons excited by electromagnetic field at the interfaces between metals and dielectric materials, show us a potentional way to settle these problems. Surface plasmon can confine the electromagnetic energy at a nanoscale volume far beyond the diffraction limit in the visible and near infrared spectrum regime. It can also be exploited for polarization manipulation in the integrated optical circuits since the coupling between the light and surface plasmon is dependent on polarization. Here we focus on the investigations of foundmental integrated quantum photonic devices based on surface plasmon, including the plasmonic direction coupler, polarizer, polarization beam splitter, and so on. Using these basic devices, we will assemble the Mach-Zehnder interferometer and Hong-Ou-Mandel interferometer to realize the single quantum bit operations and some basic two-photon quantum controlled logic gates. Our investigation will find potential usage in the future integrated quantum photonic chips.

集成量子光学芯片可能成为未来量子计算和量子通信网络的核心器件。目前量子光学芯片的研究主要基于普通波导结构，波导尺寸较大，而且很难控制光的偏振信号，而偏振在量子光学的研究中具有非常重要的作用。最近我们的研究发现，表面等离子体光学不仅可以突破衍射极限，利用亚波长尺度的波导来传输和控制光学信号，而且在集成化偏振器件的设计和加工上具有独特的优势，这为实现集成化程度更高的量子光学芯片提供了一个新的思路。本项目将从表面等离子体微纳结构出发，研制集成量子光学的基本元器件，尤其是集成化偏振器件。主要内容为利用表面等离子体天线改善单光子源性能，研究表面等离子体波导传输偏振信息的基本特性，设计、加工基于表面等离子体的波导分束器，检偏器，偏振分束器等，组装制备经典和量子干涉仪，实现若干单量子比特和双量子比特操作，探索集成化量子光学芯片实现的可能性。

表面等离激元光学是光学和电子学在纳米尺度的连接桥梁，是一个新兴的研究领域，在国际上日益引起人们的关注。表面等离激元光学不仅可以突破衍射极限，利用纳米尺度的波导来传输和控制光学信号，而且在集成化偏振器件的设计和加工上具有独特的优势，这为实现集成化程度更高的量子光学芯片提供了一个新的思路。本项目基于表面等离激元微纳光学结构，研究了小型化、集成化的量子集成光学元器件，并探讨了其用于大规模量子光学计算所面临的问题和挑战，具体研究内容包括：设计和加工了集成宽带吸收器、信息编码转换器、分束比连续可调的分束器等基本元器件，在此基础上实现了表面等离激元的量子干涉，研究了表面等离激元的波色子特性，证明其可以作为量子信息的载体，并充分讨论了表面等离激元的固有损耗对量子干涉可见度的影响，为下一步基于表面等离激元的量子集成光学发展奠定了基础；在表面等离激元微纳波导结构中实现了量子偏振纠缠态的传输，探讨了实现表面等离激元量子成像的可能性；提出了片上量子信息过程中新的波导模式编码自由度，并实现了波导模式纠缠态和偏振、路径纠缠态的相干转换；利用表面等离激元天线，对量子点光源的辐射方向进行了调制等。这些研究为进一步探索表面等离激元结构在量子信息领域中的研究，开发其在未来量子信息器件中的可能应用起到了推动作用。