Verification of finite size continuous-variable quantum key distribution under coherent attacks

• Applicants: Professor Dr. Roman Schnabel; Professor Dr. Reinhard F. Werner
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 249157115

• Final Report Year: 2016

Final Report Abstract

Secret communication over public channels is one of the central pillars of a modern information society. Using quantum key distribution this is achieved without relying on the hardness of mathematical problems which might be compromised by improved algorithms or by future quantum computers. State-of-the-art quantum key distribution requires composable security against coherent attacks for a finite number of distributed quantum states as well as robustness against implementation side-channels. In this project we realised the first implementation of continuous-variable quantum key distribution satisfying these requirements. Our implementation was based on the distribution of continuous-variable Einstein-Podolsky- Rosen entangled light. It was one-sided device independent, which means the security of the generated key is not only independent of any attacks on the channels, but additionally also independent of any memory-free attacks on the detector at the remote receiver’s site. A crucial issue for the protocol is low decoherence on the distributed Einstein-Podolsky-Rosen entangled states of light. Due to optical loss, a transmission in standard telecommunication fibres is currently limited to about 4 km. It is currently not clear whether future theoretical work can make the proof more robust against optical loss. This project targeted the issue of decoherence by researching the quantum information protocol called ‘entanglement distillation’. A rather promising result of this project is that different from what was thought before, an efficient distillation of entangled states is possible without quantum memories. Since continuous-variable encoding is compatible with conventional optical communication technology, the result of this project is a significant step towards practical implementations of quantum key distribution with state-of-the-art security based solely on telecom components.

Publications

• Implementation of continuous-variable quantum key distribution with composable and onesided-device-independent security against coherent attacks, Nat. Commun. 6:8795 (2015)
  Tobias Gehring, Vitus Händchen, Jörg Duhme, Fabian Furrer, Torsten Franz, Christoph Pacher, Reinhard F. Werner, and Roman Schnabel
  
• Efficient entanglement distillation without quantum memory, Nat. Commun. 7:11720 (2016)
  Daniela Abdelkhalek, Mareike Syllwasschy, Nicolas J. Cerf, Jaromir Fiurášek, and Roman Schnabel