Tools for bringing Quantum Communication to Optical Networks

量子通信使用量子力学来解决通信任务。其中一些任务是传统的交流方式无法完成的。这方面的突出例子是量子密钥分发（QKD），它在遥远的位置创建秘密密钥，从而允许可证明的秘密通信。其他任务可以通过量子方式更有效地解决。文献中有一些有趣的应用可以在理想的量子通信网络上运行。然而，目前尚不清楚如何在短期和中期可用的有限量子通信网络上运行大多数应用程序。

Quantum Communication uses quantum mechanics to solve communication tasks. Some of these tasks cannot be achieved by classical communication. The prominent example for this is Quantum Key Distribution (QKD) which creates secret key at distant locations, thus allowing provable secret communication. Other tasks can be solved more efficiently the quantum way. There are interesting applications in the literature that could run on an ideal quantum communication network. However, it is not known how to run most of the applications on the limited quantum-enabled communication networks that are available to us in the short and medium term. Optical Communication networks readily support quantum mechanical features, for example by using laser pulses. However, abstract protocols are formulated using an idealized quantum network that sends the generalization of classical bits, the qubits, while the practical optical communication networks use laser pulses, which form a restricted set of quantum signals. We will enlarge the range of applications that can be run on a quantum-enabled optical communication network. We will reveal the fundamental problems that arise in this adaptation to optical networks. This involves on one hand to identify what quantum mechanical effects are at the heart of the quantum advantage in abstract protocols, and on the other hand to analyze whether this effects can be exploited using the quantum mechanical signal structure that is accessible in practical optical network implementations. Knowing both sides, we will then develop general tools to match them. Such customized and optimized mapping of quantum protocols to available physical systems accelerates the possibility of their practical implementation, and enables more efficient use of available resources. The same approach led point-to-point QKD to high-speed implementations that successfully abandoned the quest to directly mimic the abstract qubit protocol. Understanding the necessary and sufficient conditions for adapting abstract qubit-inspired communication protocols to optical networks is an important step in assessing their eventual commercial viability.