Security of differential quadrature phase shift quantum key distribution
Shun Kawakami, University of Tokyo
One of the simplest methods for implementing quantum key distribution over fiber-optic communication is the Bennett-Brassard 1984 protocol with phase encoding (PE-BB84 protocol), in which the sender uses phase modulation over double pulses from a laser and the receiver uses a passive delayed interferometer. Using essentially the same setup and by regarding a train of many pulses as a single block, one can carry out the so-called differential quadrature phase shift (DQPS) protocol, which is a variant of differential phase shift (DPS) protocols.
Recently, we have proved the security of DQPS protocol and shown that the secure key rate of the DQPS protocol is eight thirds as high as the rate of the PE-BB84 protocol (https://arxiv.org/abs/1512.08129). In this talk, I will introduce the background of DPS protocols, and give the brief sketch of security proof of DQPS protocol as well as discuss its practical importance.