Parametric down-conversion with local operation and two-way classical communication

The decoy-state quantum key distribution protocol suggested by Adachi et al. (Phys. Rev. Lett. 99 180503 (2007)) is proven to be secure and feasible with current techniques. It owns two attractive merits, i.e., its longer secure transmission distance and more convenient operation design. In this paper, we first improve the protocol with the aid of local operation and two-way classical communication (2-LOCC). After our modifications, the secure transmission distance is increased by about 20 km, which will make the protocol more practicable.