Decoy-state quantum key distribution using homodyne detection

In this paper, we propose to use the decoy-state technique to improve the security of the quantum key distribution (QKD) systems based on homodyne detection against the photon number splitting attack. The decoy-state technique is a powerful tool that can significantly boost the secure transmission range of the QKD systems. However, it has not yet been applied to the systems that use homodyne detection. After adapting this theory to the systems based on homodyne detection, we quantify the secure performance and transmission range of the resulting system.

Figure 1

GLLP transmission rate $\left(R\right)$ for the homodyne detection system.

Figure 2

Secure transmission rate $\left(R\right)$ vs channel length $\left(l\right)$ with $\mu =1.65$ and $x=0.9$.

Figure 3

Secure transmission rate $\left(R\right)$ vs channel length with $\mu =1.65$ and $x=2$.

Figure 4

(Color online) Minimum, optimum, and maximum channel lengths, respectively, from bottom to top for different values of threshold $\left(x\right)$.

Figure 5

Maximum transmission rate $\left(R\right)$ for the different values of the threshold $\left(x\right)$.

Figure 6

(Color online) Block diagram of the weak coherent pulse quantum key distribution system using balanced homodyne detection. EAM: electroabsorbent modulator, PR: polarization rotator, OA: optical attenuator, PM: phase modulator (Mach-Zehnder type), C: 3 dB coupler, PC: polarization controller, PS: phase shifter, PBS: polarization beam splitter (combiner), and SMWC: single mode wideband coupler.

Figure 7

Transmission rate $\left(R\right)$ vs $\mu$ for the threshold at zero, $x=0$.