Full Characterization of the Quantum Effects of Light after Transmission through the Atmosphere

项目延期提案的主要目的是“光通过大气传输后的量子效应的全面表征”，并基于我们的第一个提案。因此，我们将继续开发有效的技术来表征大气条件下光的量子态。延长期18个月的研究计划主要分为大气湍流对多方非经典性和多方纠缠的影响两个部分。首先，我们希望进一步发展通过湍流介质后非经典辐射特性的表征技术。在这种情况下，我们将采用多模非经典矩的方法来适应大气湍流损失的情况。此外，我们计划研究包含量子态全部信息的光的多部非经典准概率。这些方法可能需要重新制定现有的测量策略，以优化它们以适应大气条件。其次，我们将对大气通道中辐射场纠缠的研究进行概括。预期的初始步骤是将我们之前对湍流损失介质中纠缠的处理推广到多方场景。为此，我们将调整多重纠缠见证的构造方法，以推断通过波动损耗通道传播后状态的多重量子相关性。第二个资助期的结果将补充我们对湍流大气中量子效应的理论分析，并将使我们更深入地了解量子光学自由空间链路中波动损失的影响。特别是，我们计划确定那些类型的量子效应是最强大的大气扰动。我们在大气量子光学方面的研究将为设计新的自由空间量子通信方法提供基础。这包括从发送方的适当数据编码，通过持续量子效应的安全数据传输，到接收方的最佳检测技术等方面。我们的目标是揭示大气条件，这甚至可以作为量子通信的资源。

The main purpose of the proposed project prolongation is the ''Full Characterization of the Quantum Effects of Light after Transmission through the Atmosphere'' and is based on our first proposal. Therefore, we will continue developing efficient techniques for characterizing the quantum state of light under atmospheric conditions. The research plan of the 18 months of prolongation period is structured into the main parts of atmospheric turbulence effects on multipartite nonclassicality and multipartite entanglement.First, we want to further develop our characterization techniques for nonclassical radiation properties after passing through a turbulent medium. In this context, we will adapt the method of multi-mode nonclassical moments to the case of atmospheric turbulent loss. Furthermore, we plan to investigate multipartite nonclassicality quasiprobabilities of light, which contain the full information on the quantum state. These methods may require to reformulate existing measurement strategies, to optimize them for atmospheric conditions. Second, we will generalize our studies of entanglement of radiation fields in atmospheric channels. The anticipated initial step is a generalization of our previous treatment of entanglement in turbulent loss media to multipartite scenarios. For that purpose we will adapt our construction methods of multipartite entanglement witnesses to infer multipartite quantum correlations of states after propagation through fluctuating-loss channels. The results of this second funding period will complement our theoretical analysis of quantum effects in the turbulent atmosphere and it will result in a deeper understanding of the impact of fluctuating losses in quantum optical free-space links. In particular, we plan to identify those types of quantum effects which are most robust against atmospheric disturbances. Our investigations in atmospheric quantum optics will yield the foundations for designing novel methods of free-space quantum communication. This includes aspects ranging from proper data encoding by the sender, secure data transfer via persisting quantum effects, towards optimal detection techniques at the receiver site. We aim at uncovering atmospheric conditions, which may even serve as a resource for quantum communication.