Biography
Tobias Gehring is CSO at Celare Quantum Communications, a quantum key distribution vendor, and at Alea Quantum Technologies, a company making quantum random number generators. He is also an Associate Professor at the Technical University of Denmark (DTU) where he researches continuous-variable quantum key distribution and quantum random number generation. The two companies are spin-off companies of DTU. Tobias received his PhD in Physics from University of Hannover, Germany, in 2013 after which he became postdoctoral researcher at DTU, and eventually Associate Professor. He has made several seminal contributions to the field of quantum cryptography and led the Danish effort in the European Quantum Communication Infrastructure initiative.
Abstract
Continuous-variable quantum key distribution (CV-QKD) has transitioned from fundamental research to a viable technology for metropolitan fiber networks. Its primary advantage lies in its compatibility with standard telecom components and its resilience to noise, allowing for seamless co-existence with data communication via wavelength division multiplexing. This tutorial provides an overview of the CV-QKD landscape, focusing on the Digital Signal Processing (DSP) techniques that have become the engine of recent experimental breakthroughs. We will discuss how algorithms adapted from coherent telecommunications—such as pilot-aided phase recovery and frequency offset estimation—function at the quantum level. Finally, I will connect these hardware developments to theoretical security proofs, highlighting how modern analysis accounts for realistic experimental noise and finite-size effects.