Entangled Quantum Key Distribution Over Two Free-Space Optical Links

Christopher Erven

Research output: Contribution to journalArticle (Academic Journal)peer-review

72 Citations (Scopus)


We report on the first real-time implementation of a quantum key distribution (QKD) system using entangled photon pairs that are sent over two free-space optical telescope links. The entangled photon pairs are produced with a type-II spontaneous parametric down-conversion source placed in a central, potentially untrusted, location. The two free-space links cover a distance of 435 m and 1,325 m respectively, producing a total separation of 1,575 m. The system relies on passive polarization analysis units, GPS timing receivers for synchronization, and custom written software to perform the complete QKD protocol including error correction and privacy amplification. Over 6.5 hours during the night, we observed an average raw key generation rate of 565 bits/s, an average quantum bit error rate (QBER) of 4.92%, and an average secure key generation rate of 85 bits/s.
Original languageEnglish
Pages (from-to) 16840-16853
JournalOptics Express
Issue number21
Publication statusPublished - 7 Oct 2008


  • QKD


Dive into the research topics of 'Entangled Quantum Key Distribution Over Two Free-Space Optical Links'. Together they form a unique fingerprint.

Cite this