Quantum Key Distribution (QKD) leverages quantum effects to address the key distribution problem. Traditionally, its use has been limited to high-tech specialist networks for dedicated, trusted partners. However, advancements in hybrid quantum-classical networks now suggest the potential for QKD-level security on a wider scale.The Isabelle Infrastructure and Insider Framework (IIIf) has demonstrated the ability to formally verify security properties in proof-of-concept QKD models. In this paper, we build on these foundations to extend the formal analysis to real-world multi-photon QKD implementations. We enhance the existing model and show how IIIf’s attack tree analysis exposes threats such as the intercept-and-resend attack and the photon-number splitting (PNS) attack. Furthermore, refinement in IIIf enables the extraction of a formal specification for decoy-state QKD, strengthening security against vulnerabilities.

In this paper we employ the Shannon channel capacity theorem and classical thermodynamic Carnot's Law to derive the kT ln 2 minimum energy dissipation per bit for a communications channel. We then extend the analysis, incorporating forward error correction (FEC) to show an asymptotic energy efficiency approach to the Carnot/Shannon limit. For the first time, we derive a generalized version of the Shannon channel capacity theorem which embraces non-Gaussian noise statistics. Finally, we apply the theory to different telecommunications technologies, thus offering commonality of absolute energy efficiency assessment.