基于自发参量下转换的光子轨道角动量量子纠缠

Quantum Entanglement with Photonic Orbital Angular Momentum Based on Spontaneous Parametric Down-Conversion

作为光子重要自由度之一,轨道角动量(OAM)在光量子信息研究中占据着重要地位。将其与偏振等光子的其他自由度相结合,可实现多自由度光量子信息处理。此外,由于其具有天然的离散高维属性,故其是开展高维量子信息处理研究的最佳自由度之一。基于自发参量下转换非线性光学过程能够便捷地获得OAM纠缠源。近年来,光子OAM量子纠缠的研究受到了广泛关注,在多自由度、高维和多光子等多个方向都取得了重要进展。然而,该领域尚有诸多悬而未决的关键科学问题亟须深入研究,包括如何实现高效高质的OAM分离,如何实现更高维度的频率转换,如何提升多自由度纠缠源的品质,如何获得更多维度、更多光子的高维纠缠态以及如何构建可行的高维量子门等。从光子OAM最基本的二维操纵着手,综述了单光子OAM量子态调控、双光子及多光子OAM纠缠操纵。围绕多自由度、大角动量和高维等特性,从生成、调控、测量及应用等角度系统讨论了光子OAM量子纠缠。同时,探索了解决本方向关键科学问题的一些可能解决途径。

As an important degree of freedom,orbital angular momentum(OAM)plays a key role in the research of photonic quantum information.Combined OAM with other degrees of freedom of photons such as polarization,multi-degree-of-freedom photonic quantum information processing is possible.In addition,due to the property of natural discrete high dimensions,OAM is one of the optimal degrees of freedom for the research of high dimensional quantum information processing.Based on the spontaneous parametric down-conversion nonlinear optical process,the entangled source with OAM can be easily obtained.In recent years,quantum entanglement based on OAM of photons has attracted wide attention and many significant progresses have been made in many directions,such as multiple degrees of freedom,high dimension and multiple photons.However,there are still many key scientific issues that need to be further studied in this realm,including how to achieve efficient and high-quality OAM sorter,how to achieve higher-dimensional frequency conversion,how to improve the quality of multi-degree-of-freedom entangled sorter,how to obtain high-dimensional entangled states with more dimensions and more photons,and how to construct feasible high-dimensional quantum gates.Starting from the most basic two-dimensional manipulation of OAM of photons,the quantum state regulation of single photon with OAM and the entanglement manipulation of two photons and multiple photons with OAM are reviewed.Based on the characteristics of multiple degrees of freedom,large angular momentum and high dimension,quantum entanglement of OAM of photons is discussed systematically from the perspectives of generation,regulation,measurement and application.Meanwhile,the possible methods to overcome the challenges in this realm are explored.