Making the decoy-state measurement-device-independent quantum key distribution practically useful

The relatively low key rate seems to be the major barrier to its practical use for the decoy-state measurement-device-independent quantum key distribution (MDI-QKD). We present a four-intensity protocol for the decoy-state MDI-QKD that hugely raises the key rate, especially in the case in which the total data size is not large. Also, calculations show that our method makes it possible for secure private communication with fresh keys generated from MDI-QKD with a delay time of only a few seconds.

Figure 1

The optimized key rates (per pulse pair) versus transmission distance by different methods with device parameters being given by line $a$ of Table 1. Here we set the total number of pulses at each side $N_t={10}^{10}$ and the failure probability $\epsilon ={10}^{-7}$.

Figure 2

The optimized key rates (per pulse pair) versus transmission distance by different methods with device parameters being given by line $b$ of Table 1. Here we set the total number of pulses at each side $N_t={10}^9$ and the failure probability $\epsilon ={10}^{-7}$.

Figure 3

The optimized key rates (per pulse pair) versus transmission distance by different methods with device parameters being given by line $b$ of Table 1. Here we set the total number of pulses at each side $N_t={10}^{11}$ and the failure probability $\epsilon ={10}^{-7}$.

Figure 4

The optimized key rates (per pulse pair) versus transmission distance by different methods with device parameters being given by line $c$ of Table 1. Here we set the total number of pulses at each side $N_t={10}^{13}$ and the failure probability $\epsilon ={10}^{-7}$.

Figure 5

The optimized key rates (per pulse pair) versus different total numbers of pulse pairs $N_t$ for each protocol at the distance of 50 km. Here the failure probability is $\epsilon ={10}^{-10}$, with the device parameters being listed in line $b$ of Table 1. We strictly use the Chernoff bound in the calculation.

Figure 6

The optimized key rates (per pulse pair) versus different total numbers of pulse pairs $N_t$ for each protocol at the distance of 50 km calculated by the normal distribution approximation. Here the failure probability is also set to be ${10}^{-10}$, with the device parameters being listed in line $b$ of Table 1.