Unconditional security at a low cost

By simulating four quantum key distribution (QKD) experiments and analyzing one decoy-state QKD experiment, we compare two data postprocessing schemes based on security against individual attack by Lütkenhaus, and unconditional security analysis by Gottesman-Lo-Lütkenhaus-Preskill. Our results show that these two schemes yield close performances. In QKD, since unconditional security is highly sought after, we conclude that one is better off considering unconditional security, rather than restricting to individual attacks.

Figure 1

(Color online) Plot of privacy amplification part of GLLP and Lütkenhaus. The maximal deviation of two curves is 15.36% when the error rate is 3.85%.

Figure 2

(Color online) Plot of the key generation rate as a function of the transmission distance, comparing two data postprocessing schemes, Lütkenhaus and GLLP. The key parameters are listed in Table . Here we consider the nondecoy case and use the optimal expected photon number $\mu =\eta$ [8]. Using Cascade protocol [30], the error correction efficiency is 1.16. Details of the QKD simulation model appear in [25].

Figure 3

(Color online) Plot of the key generation rate as a function of the transmission distance for decoy state QKD, comparing Lütkenhaus and GLLP. The key parameters are listed in Table . Using the Cascade protocol [30], the error correction efficiency is 1.16. Here we assume the efficiency of privacy amplification is 1. Details of QKD simulations can be seen in [25].