Thomas Scheidl

Quantum Key Distribution (QKD) is a fast growing scientific as well as commercial field. Governments as well as private businesses seek for enhanced security solutions that can withstand future hacking attacks on classical cryptographic protocols. Today, there exists a vast amount of different QKD protocols that claim to offer “unconditional” security. However, looking in more detail many subtleties lead to different security levels, or in worst-case scenarios to no security at all. Thus, it is of upmost importance to appropriately select and design QKD protocols and networks. In this work (presented as a poster), we present and compare three different QKD protocols, concerning their security, key-rate performance, and applicability especially for satellite-based QKD networks. Our main results from this study are presented and we introduce the key requirements and the basic workflow of the design and optimization of a trusted-node based and free European QKD network. Finally, realistic satellite missions and their expected secure key rates in various situations are presented.

Quantum Key Distribution (QKD) allows unconditionally secure communication based on the laws of quantum mechanics rather then assumptions about computational hardness. Optimizing the operation parameters of a given QKD implementation is indispensable in order to achieve high secure key rates. So far, there exists no model that accurately describes entanglement-based QKD with continuous-wave pump lasers. For the first time, we analyze the underlying mechanisms for QKD with temporally uniform pair-creation probabilities and develop a simple but accurate model to calculate optimal trade-offs for maximal secure key rates. In particular, we find an optimization strategy of the source brightness for given losses and detection-time resolution. All experimental parameters utilized by the model can be inferred directly in standard QKD implementations, and no additional assessment of device performance is required. Comparison with experimental data shows the validity of our model. Our results yield a tool to determine optimal operation parameters for already existing QKD systems, to plan a full QKD implementation from scratch, and to determine fundamental key rate and distance limits of given connections.