Fig. 1. Scheme of the NPP TF-QKD

Fig. 2. Symmetric (sym) and asymmetric (asym) NPP TF-QKD's secret key rate versus channel total loss with different dark count rate

Fig. 3. Symmetric and asymmetric NPP TF-QKD's secret key rate versus transmission distance with different dark count rate

Fig. 4. NPP TF-QKD's secret key rate versus transmission distance under symmetric channels with different $\sigma$ and$P_{\mathrm{d}}={\mathrm{10}}^{-\mathrm{8}}$

Fig. 5. NPP TF-QKD's secure key rate versus distance under symmetric channels with different $\sigma$ and $P_{\mathrm{d}}={\mathrm{10}}^{-\mathrm{7}}$