Avetisyan H, Monken C H
Opt Express. 2016 Feb 8;24(3):2318-35. doi: 10.1364/OE.24.002318.
Higher order correlation beams, that is, two-photon beams obtained from the process of spontaneous parametric down-conversion pumped by Hermite-Gauss or Laguerre-Gauss beams of any order, can be used to encode information in many modes, opening the possibility of quantum communication with large alphabets. In this paper we calculate, analytically, the fourth-order correlation function for the Hermite-Gauss and Laguerre-Gauss coherent and partially coherent correlation beams propagating through a strong turbulent medium. We show that fourth-order correlation functions for correlation beams have, under certain conditions, expressions similar to those of intensities of classical beams and are degraded by turbulence in a similar way as the classical beams. Our results can be useful in establishing limits for the use of two-photon beams in quantum communications with larger alphabets under atmospheric turbulence.
高阶关联光束，即通过任意阶厄米 - 高斯光束或拉盖尔 - 高斯光束泵浦的自发参量下转换过程获得的双光子光束，可用于在多种模式下编码信息，从而开启了使用大字母表进行量子通信的可能性。在本文中，我们通过解析计算了厄米 - 高斯光束和拉盖尔 - 高斯光束的相干及部分相干关联光束在强湍流介质中传播时的四阶关联函数。我们表明，在某些条件下，关联光束的四阶关联函数具有与经典光束强度相似的表达式，并且与经典光束一样会因湍流而退化。我们的结果对于确定在大气湍流条件下使用大字母表进行量子通信时双光子光束的使用限制可能会有所帮助。
