Time bin quantum key distribution protocols for free space communications

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Quantum key distribution (QKD) is a promising technology to enable secure cryptography after quantum computers have been developed. It allows for a key growing protocol that permits creating absolutely random keys to be used in the onetime pad codification scheme. Enabling a global QKD network is one of the final goals of the field. However, to do this with conventional optical fibres presents a fundamental limitation due to their intrinsic loss. Free-space, and specifically satellite links, have been proposed as an alternative and have gathered a lot of interest in recent years. They are considered one of the best candidates to enable a global network. Free-space QKD implementations are dominated by polarisation encoding protocols due to the relative transparency of the atmosphere to polarization. Nonetheless, time-bin and phase codifications offer some advantages and can be practical thanks to new passive interferometer designs. In this paper, the first free-space Coherent One-Way (COW) implementation is reported, some design considerations are commented, and the results of the experiment are shown. These show how time-bin/phase codifications are interesting candidates for free-space QKD.
Original languageEnglish
Title of host publicationQuantum Communications and Quantum Imaging XX
EditorsKeith S. Deacon, Ronald E. Meyers
ISBN (Electronic)9781510654617
ISBN (Print)978151065460
Publication statusPublished - 4 Oct 2022

Publication series

NameProceedings of SPIE
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


  • atmospheric turbulence
  • free-space quantum key distribution
  • quantum communication
  • quantum technology
  • singlephoton detection
  • time-bin QKD

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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