Time coding protocols for quantum key distribution (16 pages)

William Boucher, Thierry Debuisschert

Chi‐Hang Fred Fung

Hu Hua-Peng, Jing Zhang, Jindong Wang +5 more

We propose one kind of improved QKD scheme based on time coding and phase coding. The pulse which had been discarded on the BB84 protocol phase coding QKD system is used to realize the time coding protocol, thus the useful bits rate in the present scheme can be doubled. At the same time, the phase coding keys and the time coding keys are obtained, we may combine both as new keys which can enhancethe generated rate and the sensitivity of monitor. At Bob’s side, a Fraday-Michelson is used instead of a traditional M-Z interferometer, which improves the stability of the interference visibility. With the proposed experimental setup, a stable quantum key distribution was performed over 90 km fiber. It is shown in our experiment that the characteristics of our system are as follows: secure, stable and economical.

Bing Qi

We establish a security proof of frequency-time coding quantum key distribution (FT-QKD) protocol by showing its connection to the squeezed state quantum key distribution protocol, which has been proven to be unconditionally secure. We also extend the prepare-and-measure FT-QKD protocol to an entanglement based FT-QKD protocol which is more appealing in practice. Furthermore, we propose a correlated frequency measurement scheme of entangled photon pair by using time resolving single photon detector. Simulation results show that the FT-QKD protocol can be implemented with today's technology.

Sheila Cobourne

Mahmoud Ahmed Othman Abu Zaid, Ramani Selvanambi