Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Practical long-distance quantum key distribution system using decoy levels



Danna Rosenberg, Charles G. Peterson, Jim A. Harrington, Patrick R. Rice, N. Dallman, K. T. Tyagi, K. P. McCabe, Sae Woo Nam, Burm Baek, Robert Hadfield, Richard J. Hughes, Jane E. Nordholt


Quantum key distribution (QKD) has the potential for widespread real-world applications, but no secure long-distance experiment has demonstrated the truly practical operation needed to move QKD from the laboratory to the real world due largely to limitations in synchronization and poor detector performance. Here, we report results obtained using a fully automated, robust QKD system based on the Bennett Brassard 1984 (BB84)protocol with low-noise superconducting nanowire single-photon detectors (SNSPDs) and decoy levels to produce a secret key with unconditional security over a record 140.6 km of optical fibre, an increase of more than a factor of five compared with the previous record for unconditionally secure key generation in a practical QKD system.
New Journal of Physics


quantum key distribution, decoy states, BB84, superconducting detectors, sspd


Rosenberg, D. , Peterson, C. , Harrington, J. , Rice, P. , Dallman, N. , Tyagi, K. , McCabe, K. , Nam, S. , Baek, B. , Hadfield, R. , Hughes, R. and Nordholt, J. (2009), Practical long-distance quantum key distribution system using decoy levels, New Journal of Physics, [online], (Accessed July 17, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created April 29, 2009, Updated October 12, 2021