Quantum cryptography for secure free-space communications

Richard J. Hughes, William T. Buttler, Paul G. Kwiat, Steve K. Lamoreaux, Gabriel G. Luther, George L. Morgan, Jane E. Nordholt, C. Glen Peterson

Research output: Contribution to journalConference articlepeer-review


The secure distribution of the secret random bit sequences known as `key' material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal photon polarization states to generate shared key material over line-of-sight optical links. Key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. We have developed and tested a free-space quantum key distribution (QKD) system over an outdoor optical path of approximately 1 km at Los Alamos National Laboratory under nighttime conditions. Results show that free-space QKD can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, we examine the feasibility of surface to satellite QKD.

Original languageEnglish (US)
Pages (from-to)98-103
Number of pages6
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 1999
Externally publishedYes
EventProceedings of the 1999 Free-Space Laser Communication Technologies XI - San Jose, CA, USA
Duration: Jan 26 1999Jan 27 1999

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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