利用光子轨道角动量纠缠态实现光束微旋转角量子精密测量

Orbital angular momentum (OAM) of photons characterizes both higher dimensions and spiral phase, and it shows a great of potential applications in quantum computation, quantum communication, quantum imaging, and attracts a lot of attentions. This project will experimentally and theoretically study generation, identification, measurement and manipulation of OAM states in optics systems and atom systems. The main research contents include the mechanism of how to generate higher dimensional OAM entangled states with high efficiency and purity, designing vortices of pumping light will be one of the candidates. Weak measurements theory with OAM pointer will be studied. Basing on this work, we hope to find the relationship between the supersensitive measurement of angular displacements and the weak measurement theory. Instead of squeezed states and multi-photon entangled states, supersensitive measurement of the angular displacements will be realized experimentally with higher dimensional OAM entangled state. These results will provide new methods for the generation of higher dimensional OAM states and reveal the mechanism of weak measurements theory with OAM pointer, also will provide a new technic to measure the angular displacement which can beat the standard quantum limit. Our program has an important impact in scientific research, especially in the field of coordinate alignment for free space communication and precision measurement of magnetic field.

光子轨道角动量（OAM）态具有高维和螺旋相位特性，在量子计算、量子通信、量子成像等领域展示出了巨大的应用潜力，引起人们高度的关注。本项目拟从光束微旋转角量子精密测量的光源出发，首先研究如何在参量下转换过程中实现高效率、高纯度、高维的光子OAM纠缠态的制备，以此作为旋转角精密测量的输入态。进一步研究弱测量理论，探索OAM态在弱测量理论的应用，具体为对光束微旋转角度的放大作用，以及该技术在微小旋转角测量过程中的分辨率和灵敏度问题。最后，我们将利用前面制备的高维OAM纠缠态，代替目前大部分测量方案所使用的压缩态或多光子纠缠态，实现光束微旋转角的量子精密测量。本项目的研究不仅对OAM纠缠态、弱测量理论以及光束微旋转角量子精密测量理论的深入研究具有重要的学术意义，同时为自由空间通信中坐标校准、磁场精密测量等重大科学应用领域提供指导价值。

具有特殊空间振幅、相位分布的结构光在精密测量、超分辨成像、计算成像等领域具有重要的应用价值。其中基于光子OAM的旋转角度测量灵敏度的问题一直是人们研究的热点，本课题研究研究了在SU(2)、SU(1,1)和混合干涉仪多种量子光场注入情况下旋转角度精度的最佳值。混合干涉仪的旋转角度灵敏度最佳值分为两种情况，四波混频在前光分束器在后的精度最佳值为1/4lN；光分束器在前四波混频在后的精度最佳值为1/2lN。关联成像系统的空间分辨率仍受限于光场的衍射效应，无法超越瑞利衍射 极限，很难从微小尺度诠释物理本质。针对单像素成像系统，我们推导并实验验证了参考光路和探测光路的点扩散函数将共同决定成像分辨率我们又利用高斯光斑和环形光斑交替照明的方式，等效实现了两光斑的差值照明，进一步改善了成像分辨率。此外，我们对成像结果运用去卷积迭代算法，最终实现了对瑞利衍射极限2.82倍的超越。基于单像素成像技术，我们实现了未知复振幅光场的振幅和相位测量。实验中利用22KHz的高速数字微镜阵列以及棋盘结构的Fourier谱采样方法，实现了103*103像素的光场复振幅成像，其中每个像素的长度为68.4微米。