Floodlight Quantum Key Distribution: A Practical Route to Gbps Secret-Key Rates

TL;DR

Floodlight QKD (FL-QKD) enables high-rate, secure quantum key distribution over long distances by flooding the channel with many photons across multiple modes, achieving gigabit-per-second secret keys with existing technology.

Contribution

The paper introduces floodlight QKD, a novel approach that significantly increases secret-key rates over long distances without requiring new technology.

Findings

FL-QKD achieves 2 Gbps over 50 km fiber link.

FL-QKD is secure against the optimum frequency-domain collective attack.

FL-QKD surpasses state-of-the-art secret-key efficiency by two orders of magnitude.

Abstract

The channel loss incurred in long-distance transmission places a significant burden on quantum key distribution (QKD) systems: they must defeat a passive eavesdropper who detects all the light lost in the quantum channel and does so without disturbing the light that reaches the intended destination. The current QKD implementation with the highest long-distance secret-key rate meets this challenge by transmitting no more than one photon per bit [Opt. Express 21, 24550-24565 (2013)]. As a result, it cannot achieve the Gbps secret-key rate needed for one-time pad encryption of large data files unless an impractically large amount of multiplexing is employed. We introduce floodlight QKD (FL-QKD), which floods the quantum channel with a high number of photons per bit distributed over a much greater number of optical modes. FL-QKD offers security against the optimum frequency-domain collective attack by transmitting less than one photon per mode and using photon-coincidence channel monitoring, and it is completely immune to passive eavesdropping. More importantly, FL-QKD is capable of a 2 Gbps secret-key rate over a 50 km fiber link, without any multiplexing, using available equipment, i.e., no new technology need be developed. FL-QKD achieves this extraordinary secret-key rate by virtue of its unprecedented secret-key efficiency, in bits per channel use, which exceeds those of state-of-the-art systems by two orders of magnitude.