page_title: DARPA Quantum Network
hierarchical_section_title: DARPA Quantum Network
caption_attribution_description: English: Entangled link - Barb - DARPA Quantum Network, in the BBN laboratory. December 2004. Created by Boston University and BBN.
context_page_description: The DARPA Quantum Network was the world's first quantum key distribution network, operating 10 optical nodes across Boston and Cambridge, Massachusetts. It became fully operational on October 23, 2003 in BBN's laboratories, and in June 2004 was fielded through dark fiber under the streets of Cambridge and Boston, where it ran continuously for over 3 years. The project also created and fielded the world's first superconducting nanowire single-photon detector. It was sponsored by DARPA as part of the QuIST program, and built and operated by BBN Technologies in close collaboration with colleagues at Harvard University and the Boston University Photonics Center.
  The DARPA Quantum Network was fully compatible with standard Internet technology, and could provide QKD-derived key material to create Virtual Private Networks, to support IPsec or other authentication, or for any other purpose. All control mechanisms and protocols were implemented in the Unix kernel and field-programmable gate arrays. QKD-derived key material was routinely used for video-conferencing or other applications.
  The DARPA Quantum Network was built in stages.
context_section_description: The DARPA Quantum Network (2002–2007) was the world's first quantum key distribution (QKD) network, operating 10 optical nodes across Boston and Cambridge, Massachusetts. It became fully operational on October 23, 2003 in BBN's laboratories, and in June 2004 was fielded through dark fiber under the streets of Cambridge and Boston, where it ran continuously for over 3 years. The project also created and fielded the world's first superconducting nanowire single-photon detector. It was sponsored by DARPA as part of the QuIST program, and built and operated by BBN Technologies in close collaboration with colleagues at Harvard University and the Boston University Photonics Center.
  The DARPA Quantum Network was fully compatible with standard Internet technology, and could provide QKD-derived key material to create Virtual Private Networks, to support IPsec or other authentication, or for any other purpose. All control mechanisms and protocols were implemented in the Unix kernel and field-programmable gate arrays. QKD-derived key material was routinely used for video-conferencing or other applications.
  The DARPA Quantum Network was built in stages. In the project's first year (year 1), BBN designed and built a full QKD system (Alice and Bob), with an attenuated laser source (~ 0.1 mean photon number) running through telecom fiber, phase-modulated via an actively stabilized Mach-Zender interferometer. BBN also implemented a full suite of industrial-strength QKD protocols based on BB84. In year 2, BBN created two 'Mark 2' versions of this system (4 nodes) with commercial-quality InGaAs detectors created by IBM Research. These 4 nodes ran continuously in BBN's laboratory from October 2003, then two were deployed at Harvard and Boston University in June 2004, when the network began running continuously across the metro Boston area, 24x7. In year 3, the network expanded to 8 nodes with the addition of an entanglement-based system (derived from work at Boston University) designed for telecom fibers, and a high-speed atmospheric (freespace) link designed and built by the National Institute of Standards and Technology. In year 4, BBN added a second freespace link to the overall network, using nodes created by Qinetiq, and investigated improved QKD protocols and detectors. Finally, in year 5, BBN added the world's first superconducting nanowire single-photon detector to the operational network. It was created by a collaboration between researchers at BBN, the University of Rochester, and the National Institute of Standards and Technology; that first 100 Mhz system ran 20x faster than any existing single-photon detector at telecom wavelengths. In that final year, BBN also collaborated with researchers at the Massachusetts Institute of Technology to implement, and experiment with, a proof-of-concept version of the world's first quantum eavesdropper (Eve).
  When fully built, the network's 10 nodes were as follows. All ran BBN's quantum key distribution and quantum network protocols so they inter-operated to achieve any-to-any key distribution.
  Alice, Bob – 5 Mhz, attenuated laser pulses through telecom fiber, phase-modulated
  Anna, Boris – 5 MHz, attenuated laser pulses through telecom fiber, phase-modulated
  Alex, Barb – entanglement based photons through telecom fiber, polarization-modulated
  Ali, Baba – approximately 400 MHz, attenuated laser pulses through the atmosphere, polarization-modulated
  Amanda, Brian – attenuated laser pulses through the atmosphere, polarization-modulated
  The DARPA Quantum Network implemented a variety of quantum key distribution protocols, to explore their properties. All were integrated into a single, production-quality protocol stack. Authentication was based on public keys, shared private keys, or a combination of the two. (The shared private keys could be refreshed by QKD-derived keys.) Privacy amplification was implemented via GF[2n] Universal Hash. Entropy estimation was based on Rényi entropy, and implemented by BBBSS 92, Slutsky, Myers / Pearson, and Shor / Preskill protocols. Error correction was implemen
caption: Barb, the entanglement-based receiver, in 2004.
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