Novel nonclassical-light-assisted protocols for quantum key distribution

The key to making quantum key distribution practical (especially for free-space applications) is to be able to use weak laser pulses (WLP) instead of single photons, while at the same time making sure that any third party wanting to avoid detection and mount an eavesdropping attack is restricted to using beam-splitting rather than photon-number splitting (PNS). In this effort, we propose a novel scheme to restrict eavesdropping to the beam-splitting attack: the use of entangled light pulses randomly mixed with the WLP, where the WLP are used exactly as in the standard BB84 protocol. The key properties of quantum non-locality guarantee an expected finite degree of entanglement measured at the end of the protocol, provided all losses are due to beam-splitter type environmental interactions (or eavesdropping), whereas any attempt to mount a PNS attack would be detected immediately since it results in a complete loss of entanglement. According to our new protocol, BB84 with WLP would be applied only when a complete loss of entanglement is not detected, thus ensuring the absence of a PNS attack, and yielding a key generation rate far more favorable than BB84 alone. BENEFIT: While quantum key distribution is very recent technology in terms of commercial acceptance, it already has a significant potential market, both within the Federal Government, and in the private sector (such as large financial institutions). As the technology matures, the market for QKD implementations can be expected to top $200M annually. At present, the development of a detailed MathSense Analytics commercialization strategy will depend on the details of the results from our Phase I effort. If Phase I is successful, we will attempt to leverage potential Phase II funding with additional commercial capital sources.